libebml is is licensed under LGPL not GPL. from the project's homepage (http://www.matroska.org/): "The source code of the libraries developed by the Matroska Development Team is licensed under GNU L-GPL."
yes, you're right. i've talked to the developers of the library via irc and was told that it has always been lgpl: 17:30:10 <~robUx4> luckyduck, it has never been GPL thanks for the report, fixed in cvs