Explicit licence for data?

[mym]

Hello,

You game is one of the best RTS I know working on Linux (native) and with an Open Source engine, many thanks for all the work you do.

I'm particularly concerned with the licence of the data.
While the source code is clearly defined as GPL, information about the data licence is not very clear.

In the licence.txt file of the data archive, we can read:

Code: [Select]

This software may be redistributed freely, but all redistributions must retain all occurences of the above copyright notice and web site addresses that are currently in place.
In the FAQ of the forum, there is a slightly different information:

Code: [Select]

What kind of license does Glest have?
Glest source code is GPL, as for the data you can do whatever you want with it as long as you credit us.
While the first information doesn't mention anything about modifying data, using them modified and broadcasting them in modified versions of the game or other Open Source projects, the second information (FAQ) *seems* to grant such permission.

This results in confusion about the global licence of the game, and game websites may set your game as partially Free Software, or even do not include your game if they only deal with Free Software (this is the case for the website jeuxlibres.net which is the biggest French directory for Free Software games).

So I wonder if you could specify an explicit licence for your data, whatever it will be.
Of course I would really prefer seeing a free licence applied, in the sense of the Free Software Foundation.
For instance, a Creative Commons BY SA would do the thing, or even a basic GPL licence.
I'm contributing to the Neverball project, every stuff of our game is under the GPL licence, and everything goes fine