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Old 2011-10-04, 18:11   #5
Mr. P-1
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Jun 2003

7·167 Posts

Originally Posted by Mr. P-1 View Post
One possible answer to 2 is "GPL with an additional restriction". This would work, (at the cost of rendering the source in this "fork" of GMP-ECM incompatible with ordinary GPL). There is however one potential trap that George should be aware of. If the distribution terms allow "GPL" to be GPLv3 (Either by specifying GPLv3 explicitly, some earlier version "or any later", or by failing to specify the version at all), then any recipient may, under the terms of GPLv3 remove the restriction, and distribute under the unrestricted terms of GPLv3.
Another possibility, which avoids the above problem is "GPL with an additional permission". Specifically, George does not put his software under GPL, but continues to distribute it under its current terms. If George does not do so, then nobody else can make his software subject to the GPL. The GMP-ECM copyright holders distribute their software under GPL with the following rider:

"As an additional permission, you may link the source (or a modified version of it) with any version (including a modified version) of George Woltman's bignum library, and distribute the resulting combined binary and/or combined sources, provided that you

1. comply fully with the licence conditions of the bignum library.

2. grant this additional permission to anyone who receives a copy.

3. comply with the terms of GPL version <foo>, to the maxim extent possible, consistent with 1 and 2 above.

You may remove this additional permission and distribute GMP-ECM under the pure terms of GPL version <foo>. However, nothing else gives you permission to link the software to George Woltman's Bignum library or to distribute the combined software. If you do not distribute the combined software in accordance with terms of this additional permission, including its requirement that you grant this additional permission to anyone who receives a copy, then you may not distribute the combined software at all."

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