README.md: GPL LICENSE problem

[frantony]

@phalox

Here is a quote from README.md (I have specially emphasize the word 'and'):

This code is released under the terms of GNU GPL v2 and GNU GPL v3.

It's is impossible to release code under GPLv2 and GPLv3 at the same time!
You can release code e.g. under either GPLv2 or GPLv3.

Here are some dual-licensed software examples:

Perl

Here is a quote from https://dev.perl.org/licenses/ :

It is free software; you can redistribute it and/or modify it under the terms of either:

a) the GNU General Public License as published by the Free Software Foundation; either version 1, or (at your option) any later version, or

b) the "Artistic License".

Ruby

Here is a quote from https://www.ruby-lang.org/en/about/license.txt :

You can redistribute it and/or modify it under either the terms of the
2-clause BSDL (see the file BSDL), or the conditions below:

[djsavvy]

See #500 -- this repository is no longer maintained

[danielinux]

You can safely disregard README.

The clarification is in COPYING, stating:

Released under the GNU General Public License, version 2, or (at your option)
version 3.

https://github.com/tass-belgium/picotcp/blob/master/COPYING

The "any later version" clause was never accepted by Altran. The original version was GPLv2, then a v3 option has been added later on (i.e. a future GPLv4 won't apply to this project unlike other projects that offer a "any later version" option).