Conflicting license information in the stdlib FFI module
"... a recipient may use your version of this file under the terms of any one of the CPL, the GPL or the LGPL."
"you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License version 3"
seems to be LGPLv3 only
ideally, all code included with JRuby should be compatible with the tri CPL/GPL/LGPL license described in COPYING