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ad9f64cd2d
Add the full text of the copyleft-next-0.3.1 license to the kernel
tree as well as the required tags for reference and tooling.
The license text was copied directly from the copyleft-next project's
git tree [0].
Discussion of using copyleft-next-0.3.1 on Linux started since June,
2016 [1]. In the end Linus' preference was to have drivers use
MODULE_LICENSE("GPL") to make it clear that the GPL applies when it
comes to Linux [2]. Additionally, even though copyleft-next-0.3.1 has
been found to be to be GPLv2 compatible by three attorneys at SUSE and
Redhat [3], to err on the side of caution we simply recommend to
always use the "OR" language for this license [4].
Even though it has been a goal of the project to be GPL-v2 compatible
to be certain in 2016 I asked for a clarification about what makes
copyleft-next GPLv2 compatible and also asked for a summary of
benefits. This prompted some small minor changes to make compatibility
even further clear and as of copyleft 0.3.1 compatibility should
be crystal clear [5].
The summary of why copyleft-next 0.3.1 is compatible with GPLv2
is explained as follows:
Like GPLv2, copyleft-next requires distribution of derivative works
("Derived Works" in copyleft-next 0.3.x) to be under the same license.
Ordinarily this would make the two licenses incompatible. However,
copyleft-next 0.3.1 says: "If the Derived Work includes material
licensed under the GPL, You may instead license the Derived Work under
the GPL." "GPL" is defined to include GPLv2.
In practice this means copyleft-next code in Linux may be licensed
under the GPL2, however there are additional obvious gains for
bringing contributions from Linux outbound where copyleft-next is
preferred. A summary of benefits why projects outside of Linux might
prefer to use copyleft-next >= 0.3.1 over GPLv2:
o It is much shorter and simpler
o It has an explicit patent license grant, unlike GPLv2
o Its notice preservation conditions are clearer
o More free software/open source licenses are compatible
with it (via section 4)
o The source code requirement triggered by binary distribution
is much simpler in a procedural sense
o Recipients potentially have a contract claim against distributors
who are noncompliant with the source code requirement
o There is a built-in inbound=outbound policy for upstream
contributions (cf. Apache License 2.0 section 5)
o There are disincentives to engage in the controversial practice
of copyleft/ proprietary dual-licensing
o In 15 years copyleft expires, which can be advantageous
for legacy code
o There are explicit disincentives to bringing patent infringement
claims accusing the licensed work of infringement (see 10b)
o There is a cure period for licensees who are not compliant
with the license (there is no cure opportunity in GPLv2)
o copyleft-next has a 'built-in or-later' provision
The first driver submission to Linux under this dual strategy was
lib/test_sysctl.c through commit
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