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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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<HTML>
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<HEAD>
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<title>What's good about the LGPL? LG #38</title>
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<BODY BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#0000AF"
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ALINK="#FF0000">
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<H4>
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"Linux Gazette...<I>making Linux just a little more fun!</I>"
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</H4>
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<P> <HR> <P>
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<center>
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<H1><font color="maroon">Why you might want to use the Library GPL for your next library</font></H1>
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<H4>By <a href="mailto:eric.kidd@pobox.com">Eric Kidd</a></H4>
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</center>
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<P> <HR> <P>
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<P>Richard Stallman, the founder of the GNU Project, recently wrote an
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article titled <A
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hREF="http://www.gnu.org/philosophy/why-not-lgpl.html">Why you shouldn't
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use the Library GPL for your next library</A>. He argued that placing new
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libraries under the regular GPL would give an advantage to free software
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authors. If you haven't read this article yet, you should. Stallman knows a
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lot about free software, and he makes several important points.</P>
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<P>I disagree with Stallman, however. His article omitted several reasons
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<EM>against</EM> using the GPL for libraries, and some of these are pretty
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important. First, GPL'd libraries can't be used in all free
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software. Second, US law probably allows proprietary software to use GPL'd
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libraries anyway. Third, GPL'd libraries may discourage people from using
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GNU/Linux systems.</P>
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<UL>
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<LI><A HREF="#free-software">GPL'd libraries can't be used by all free
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software</A>
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<LI><A HREF="#proprietary">Proprietary applications may be able to use GPL'd
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libraries anyway</A>
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<LI><A HREF="#discourage">GPL'd libraries may discourage people from using
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GNU/Linux</A>
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<LI><A HREF="#which">So I'm a free software author? Which license should I
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use?</A>
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</UL>
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<H2><A NAME="free-software">GPL'd libraries can't be used by all free
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software</A></H2>
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<P>I'm really lucky--I write free software for a living. When I decided to
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stop writing proprietary software, my paycheck got cut in half. (Don't
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worry; I'll find a way to earn it all back.) My new employer pays me to
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enhance a mail server used by several colleges. I also do consulting work,
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since it pays well. All the code I write can be used in GPL'd programs, but
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very little of it is released under the GPL itself.</P>
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<P>Even though I write nothing but free software, my programs can't link
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against a GPL'd library. A GPL'd library can only be used in a GPL'd
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program. Programs using the X11, BSD, Netscape, Mozilla or Artistic
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Licenses cannot use GPL'd libraries. (Several of these licenses are flawed,
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but that's another topic.)</P>
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<P>My employer's mail server uses a <A HREF="#bsd-note">BSD-style</A>
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license. I don't have the necessary influence to make them use the
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GPL. Unfortunately, this means that I can't use GPL'd libraries to make the
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program better. Instead of doing something useful for the free software
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community, I waste time reimplementing broken versions of pre-existing
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libraries. My time would be better spent adding new features to the mail
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server, or even enhancing an LGPL'd library.</P>
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<P>So in this case, using the GPL for libraries can actually <EM>hurt</EM> free
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software. It's not a simple issue.</P>
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<P><STRONG>Update:</STRONG> RMS posted the following message to the
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gnome-list:</P>
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<BLOCKQUOTE>
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<PRE>
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This exception would be redundant, because simple non-copyleft
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licenses such as X11 and BSD are compatible with the GPL already.
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So if you want to write a non-copylefted application, release it under
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the X11 license, and link it with a GPL-covered library, that is
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allowed. The linked executable would be covered by the GPL, of
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course, but the app source code would be covered by the X11 license
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alone.
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</PRE>
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</BLOCKQUOTE>
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<P>So XFree86-licensed code can use GPL'd libraries. The BSD license might
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conflict with the GPL until the <A HREF="#bsd-note">advertising clause</A>
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is removed, but this is a good thing to do anyway. However, code using the
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NPL, MPL or a similar license would still have problems. Thanks to gsv for
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pointing this out to me.</P>
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<H2><A NAME="proprietary">Proprietary applications may be able to use GPL'd
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libraries anyway</A></H2>
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<P>The GPL is well-written, and most of it would stand up in court. (The
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GPL has never been tested, probably because Stallman's legal volunteers
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have convinced violators to settle out of court.) For better or for worse,
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however, there's a good chance that proprietary software can use GPL'd
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libraries even though the license forbids this.</P>
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<P>The GPL is enforced using copyright law. The United States (and many
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other countries) have exceptions to copyright law for "fair use". Two
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important kinds of fair use involve compatibility and reverse
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engineering.</P>
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<P>Imagine that you want to write a program for Windows, but that you need
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to use an undocumented API. Microsoft won't give you the information, so
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you'll have to find it on your own. US law normally allows you to
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disassemble parts of Windows and call secret functions, even if Microsoft
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says you can't. Similarly, Microsoft can't prevent the Samba team from
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reverse-engineering Windows file sharing.</P>
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<P>Imagine that you sell proprietary software for Linux. You want to use
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the Readline library if it's present on a user's system, but the Readline
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library is GPL'd. So you decide not to ship Readline yourself. Instead, you
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fix your program to <EM>look</EM> for Readline and ask your users to
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install it on their own. (RedHat 5.2, for example, installs Readline by
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default.)</P>
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<P>Have you broken the law? You haven't made copies of Readline for anyone,
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and the GPL doesn't stop you from copying your own program. You used
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Readline yourself, but the GPL doesn't forbid this. (Even if the GPL
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<EM>did</EM> try to forbid this, it would probably fall under the "fair
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use" exemption.) Your users might choose link your program against
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Readline, but US law probably allows them to do so (and the GPL doesn't
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even try to stop them).</P>
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<P>So what prevents Readline from being used by proprietary software? Is
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your program a "derivate work" of Readline, and therefore covered by the
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GPL? Not likely, since it doesn't include any Readline code. Does
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<CODE>#including</CODE> the Readline headers subject your program to the
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GPL? Probably not--a good lawyer would claim that this is the same as
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"reverse engineering for the purposes of interoperability". Maybe you'd
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have to retype the headers in a cleanroom environment, but that's not too
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hard for a small library.</P>
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<P>So can a proprietary application dynamically link to a GPL'd library?
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Maybe. But if a proprietary application <EM>can't</EM> used a GPL'd
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library, then Microsoft may be able to cause trouble for WINE and
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Samba. This knife cuts both ways.</P>
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<P>Please remember--I am <EM>not</EM> a lawyer, and you shouldn't take
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anything I say as legal advice. Hire a professional.</P>
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<H2><A NAME="discourage">GPL'd libraries may discourage people from using
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GNU/Linux</A></H2>
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<P>In the past twelve months, lots of people have started to look at Linux.
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It's cheap, it's free (speech, not beer) and it runs all their Unix
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applications. Really, there aren't many reasons against using Linux.</P>
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<P>But let's pretend that most libraries for Linux are GPL'd. All of a
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sudden, you need to write GPL'd programs, or choose a different operating
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system. Unix vendors don't tell you what license to use. Not even Microsoft
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tries to tell you what license to use for your software.</P>
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<P>As much as I love Linux, the choice is easy. Everybody I know would throw
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out their Linux servers, and migrate to Solaris or Windows NT. Not good.
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Saying "to use our product, you must use our license" is pushy, and not
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many people would agree.</P>
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<H2><A NAME="which">So I'm a free software author? Which license should I
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use?</A></H2>
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<P>It's your library. Think about the issues, and do whatever you want.</P>
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<HR>
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<P><A NAME="bsd-note"><STRONG>Note about the BSD License</STRONG>:</A> The
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BSD license contains an "advertising" clause, which can cause <A
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HREF="http://www.gnu.org/philosophy/bsd.html">all sorts of stupid
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problems</A>. If all goes well, my employers will drop this clause from
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their license soon.</P>
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<!--===================================================================-->
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<P> <hr> <P>
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<center><H5>Copyright © 1999, Eric Kidd <BR>
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Published in Issue 38 of <i>Linux Gazette</i>, March 1999</H5></center>
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