[Trisquel-users] "Red Eclipse" free as in freedom?

[vitacell]

Hi, it is "Red Eclipse" game fully Free(as in freedom" Libre software? as I  
can see, it uses a zlib licence, which is compatible with GPL. If it is  
libre, why not to add this wonderful game to Trisquel's repositories, this  
game look nice, very customizable and doesn't need a powerful computer and  
powerful GPU.

http://redeclipse.net/wiki/License