docs/busybox.net/license.html - busybox - Git at Google

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 <p>
 <h3>BusyBox is licensed under the GNU General Public License, version 2</h3>

 <p>BusyBox is licensed under <a href="http://www.gnu.org/licenses/gpl.html#SEC1">the
 GNU General Public License</a> version 2, which is often abbreviated as GPLv2.
 (This is the same license the Linux kernel is under, so you may be somewhat
 familiar with it by now.)</p>

 <p>A complete copy of the license text is included in the file LICENSE in
 the BusyBox source code.</p>

 <p><a href="/products.html">Anyone thinking of shipping BusyBox as part of a
 product</a> should be familiar with the licensing terms under which they are
 allowed to use and distribute BusyBox.  Read the full test of the GPL (either
 through the above link, or in the file LICENSE in the busybox tarball), and
 also read the <a href="http://www.gnu.org/licenses/gpl-faq.html">Frequently
 Asked Questions about the GPL</a>.</p>

 <p>Basically, if you distribute GPL software the license requires that you also
 distribute the source code to that GPL-licensed software.  So if you distribute
 BusyBox without making the source code to the version you distribute available,
 you violate the license terms, and thus infringe on the copyrights of BusyBox.
 (This requirement applies whether or not you modified BusyBox; either way the
 license terms still apply to you.)  Read the license text for the details.</p>

 <h3>A note on GPL versions</h3>

 <p>Version 2 of the GPL is the only version of the GPL which current versions
 of BusyBox may be distributed under.  New code added to the tree is licensed
 GPL version 2, and the project's license is GPL version 2.</p>

 <p>Older versions of BusyBox (versions 1.2.2 and earlier, up through about svn
 16112) included variants of the recommended "GPL version 2 or (at your option)
 later versions" boilerplate permission grant.  Ancient versions of BusyBox
 (before svn 49) did not specify any version at all, and section 9 of GPLv2
 (the most recent version at the time) says those old versions may be
 redistributed under any version of GPL (including the obsolete V1).  This was
 conceptually similar to a dual license, except that the different licenses were
 different versions of the GPL.</p>

 <p>However, BusyBox has apparently always contained chunks of code that were
 licensed under GPL version 2 only.  Examples include applets written by Linus
 Torvalds (util-linux/mkfs_minix.c and util_linux/mkswap.c) which stated they
 "may be redistributed as per the Linux copyright" (which Linus clarified in the
 2.4.0-pre8 release announcement in 2000 was GPLv2 only), and Linux kernel code
 copied into libbb/loop.c (after Linus's announcement).  There are probably
 more, because all we used to check was that the code was GPL, not which
 version.  (Before the GPLv3 draft proceedings in 2006, it was a purely
 theoretical issue that didn't come up much.)</p>

 <p>To summarize: every version of BusyBox may be distributed under the terms of
 GPL version 2.  New versions (after 1.2.2) may <b>only</b> be distributed under
 GPLv2, not under other versions of the GPL.  Older versions of BusyBox might
 (or might not) be distributable under other versions of the GPL.  If you
 want to use a GPL version other than 2, you should start with one of the old
 versions such as release 1.2.2 or SVN 16112, and do your own homework to
 identify and remove any code that can't be licensed under the GPL version you
 want to use.  New development is all GPLv2.</p>

 <h3>License enforcement</h3>

 <p>BusyBox's copyrights are enforced by the <a
 href="http://www.softwarefreedom.org">Software Freedom Law Center</a>
 (you can contact them at gpl@busybox.net), which
 "accepts primary responsibility for enforcement of US copyrights on the
 software... and coordinates international copyright enforcement efforts for
 such works as necessary."  If you distribute BusyBox in a way that doesn't
 comply with the terms of the license BusyBox is distributed under, expect to
 hear from these guys.  Their entire reason for existing is to do pro-bono
 legal work for free/open source software projects.  (We used to list people who
 violate the BusyBox license in <a href="/shame.html">The Hall of Shame</a>,
 but these days we find it much more effective to hand them over to the
 lawyers.)</p>

 <p>Our enforcement efforts are aimed at bringing people into compliance with
 the BusyBox license.  Open source software is under a different license from
 proprietary software, but if you violate that license you're still a software
 pirate and the law gives the vendor (us) some big sticks to play with.  We
 don't want monetary awards, injunctions, or to generate bad PR for a company,
 unless that's the only way to get somebody that repeatedly ignores us to comply
 with the license on our code.</p>

 <h3>A Good Example</h3>

 <p>These days, <a href="http://www.linksys.com/">Linksys</a> is
 doing a good job at complying with the GPL, they get to be an
 example of how to do things right.  Please take a moment and
 check out what they do with
 <a href="http://www.linksys.com/servlet/Satellite?c=L_Content_C1&childpagename=US%2FLayout&cid=1115416836002&pagename=Linksys%2FCommon%2FVisitorWrapper">
 distributing the firmware for their WRT54G Router.</a>
 Following their example would be a fine way to ensure that you
 have also fulfilled your licensing obligations.</p>

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	<p>
	<h3>BusyBox is licensed under the GNU General Public License, version 2</h3>

	<p>BusyBox is licensed under <a href="http://www.gnu.org/licenses/gpl.html#SEC1">the
	GNU General Public License</a> version 2, which is often abbreviated as GPLv2.
	(This is the same license the Linux kernel is under, so you may be somewhat
	familiar with it by now.)</p>

	<p>A complete copy of the license text is included in the file LICENSE in
	the BusyBox source code.</p>

	<p><a href="/products.html">Anyone thinking of shipping BusyBox as part of a
	product</a> should be familiar with the licensing terms under which they are
	allowed to use and distribute BusyBox. Read the full test of the GPL (either
	through the above link, or in the file LICENSE in the busybox tarball), and
	also read the <a href="http://www.gnu.org/licenses/gpl-faq.html">Frequently
	Asked Questions about the GPL</a>.</p>

	<p>Basically, if you distribute GPL software the license requires that you also
	distribute the source code to that GPL-licensed software. So if you distribute
	BusyBox without making the source code to the version you distribute available,
	you violate the license terms, and thus infringe on the copyrights of BusyBox.
	(This requirement applies whether or not you modified BusyBox; either way the
	license terms still apply to you.) Read the license text for the details.</p>

	<h3>A note on GPL versions</h3>

	<p>Version 2 of the GPL is the only version of the GPL which current versions
	of BusyBox may be distributed under. New code added to the tree is licensed
	GPL version 2, and the project's license is GPL version 2.</p>

	<p>Older versions of BusyBox (versions 1.2.2 and earlier, up through about svn
	16112) included variants of the recommended "GPL version 2 or (at your option)
	later versions" boilerplate permission grant. Ancient versions of BusyBox
	(before svn 49) did not specify any version at all, and section 9 of GPLv2
	(the most recent version at the time) says those old versions may be
	redistributed under any version of GPL (including the obsolete V1). This was
	conceptually similar to a dual license, except that the different licenses were
	different versions of the GPL.</p>

	<p>However, BusyBox has apparently always contained chunks of code that were
	licensed under GPL version 2 only. Examples include applets written by Linus
	Torvalds (util-linux/mkfs_minix.c and util_linux/mkswap.c) which stated they
	"may be redistributed as per the Linux copyright" (which Linus clarified in the
	2.4.0-pre8 release announcement in 2000 was GPLv2 only), and Linux kernel code
	copied into libbb/loop.c (after Linus's announcement). There are probably
	more, because all we used to check was that the code was GPL, not which
	version. (Before the GPLv3 draft proceedings in 2006, it was a purely
	theoretical issue that didn't come up much.)</p>

	<p>To summarize: every version of BusyBox may be distributed under the terms of
	GPL version 2. New versions (after 1.2.2) may <b>only</b> be distributed under
	GPLv2, not under other versions of the GPL. Older versions of BusyBox might
	(or might not) be distributable under other versions of the GPL. If you
	want to use a GPL version other than 2, you should start with one of the old
	versions such as release 1.2.2 or SVN 16112, and do your own homework to
	identify and remove any code that can't be licensed under the GPL version you
	want to use. New development is all GPLv2.</p>

	<h3>License enforcement</h3>

	<p>BusyBox's copyrights are enforced by the <a
	href="http://www.softwarefreedom.org">Software Freedom Law Center</a>
	(you can contact them at gpl@busybox.net), which
	"accepts primary responsibility for enforcement of US copyrights on the
	software... and coordinates international copyright enforcement efforts for
	such works as necessary." If you distribute BusyBox in a way that doesn't
	comply with the terms of the license BusyBox is distributed under, expect to
	hear from these guys. Their entire reason for existing is to do pro-bono
	legal work for free/open source software projects. (We used to list people who
	violate the BusyBox license in <a href="/shame.html">The Hall of Shame</a>,
	but these days we find it much more effective to hand them over to the
	lawyers.)</p>

	<p>Our enforcement efforts are aimed at bringing people into compliance with
	the BusyBox license. Open source software is under a different license from
	proprietary software, but if you violate that license you're still a software
	pirate and the law gives the vendor (us) some big sticks to play with. We
	don't want monetary awards, injunctions, or to generate bad PR for a company,
	unless that's the only way to get somebody that repeatedly ignores us to comply
	with the license on our code.</p>

	<h3>A Good Example</h3>

	<p>These days, <a href="http://www.linksys.com/">Linksys</a> is
	doing a good job at complying with the GPL, they get to be an
	example of how to do things right. Please take a moment and
	check out what they do with
	<a href="http://www.linksys.com/servlet/Satellite?c=L_Content_C1&childpagename=US%2FLayout&cid=1115416836002&pagename=Linksys%2FCommon%2FVisitorWrapper">
	distributing the firmware for their WRT54G Router.</a>
	Following their example would be a fine way to ensure that you
	have also fulfilled your licensing obligations.</p>

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