Cop right on default maps

[Navras]

Ok I have searched and i have found some different answers so I though it would be best just to ask.

Are the default maps (atcs, tremor, transit etc) licensed under the creative commons act? http://creativecommons.org/licenses/by-sa/2.5/

what I'm really wondering is can I add things to them and work on them?

[Undeference]

http://svn.icculus.org/*checkout*/tremulous/trunk/COPYING
The map pk3s contain text files with notices along the lines of

This map uses the Tremulous media license. See the file COPYING for more

details.

(from map-tremor-1.1.0.pk3/tremor.txt)
Many of the maps do not include the .map file though.