Isn it illegal to relicense GPL code?
No, because we hold the copyright to the original WebMessenger code on which Centova Messenger is based. (The author of WebMessenger owns Centova Technologies). The copyright holder for any work may relicense his work under any other license, regardless of any licenses it was previously released under. (Other developers do not have the same right, of course, because they do not hold the copyright for our code.) Refer to the GNU GPL FAQ for more information.