Licensing uniformity: dual-license rbot core under MIT+acknowledgement and GPLv2

[rbot] / COPYING

rbot the Ruby IRC bot

Copyright (C) 2007-2008 Giuseppe Bilotta and the rbot development team

This program is free software; you can redistribute it and/or modify it
under the terms of the MIT license with acknolwedgement clause (see
COPYING.rbot) or the GNU General Public License, version 2 (see GPLv2)