[strongSwan-dev] Diffie Hellman Group 24 Question

Martin Willi martin at strongswan.org
Fri Mar 12 16:49:07 CET 2010

Hi Joy,

> Could you clarify whether strongswan is distributed under GPLv2 or MIT
> X11 license?

strongSwan is, and ever will be distributed under the GPL. Some parts
might have an additional MIT license, but the whole package is GPLv2
licensed. The liberal MIT license is compatible to the GPL.

We have invested many many full time man years of development without
any significant contributions from third parties. As other open source
projects do, we therefore sell commercial licenses of the code we fully
own (the IKEv2 daemon and its library). This helps us to keep the
project rolling.

The commercial licensing requires that we have the right to license this
code. Other projects (such as MySQL) require that you assign them the
full right on your contributions; we have chosen a more practical
approach to this problem by requesting a MIT license to any contribution
affecting parts subject to commercial licensing.

> To add dh group 24, changes would occur to existing files under

> src/charon,

Code to charon (and to some of its plugins) are affected by this rule.
If you're changes are significant (not just some single lines/changes),
you'll have to submit the code under the MIT license.

> src/libstrongswan

Same for libstrongswan. The gmp plugin itself is not part of commercial
licensing, as it is (at least historically) based on pluto code. Submit
code to the libstrongswan core under MIT, gmp plugin code under GPLv2+.

> src/pluto

We do not have the right to relicense Pluto anyway, so submit it under a
GPLv2+ license.

To contribute patches with a MIT license, please add the MIT license
with your copyright just beneath the GPL header in a source file. As
said, this is only needed if your patch exceeds a few lines and is
relevant to the copyright question at all.

Additionally, it helps if you git-format-patch your changeset with
proper author information.

Kind regards

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