I don't know, I think Legate Damar is partly right.
I wouldn't want to use Saga's Vega prime for something else in my Saga mod. Because this planet is featured prominently in the game, you fly near it in quite some missions, it is featured in cutscenes and it is talked about all the time during the Vega missions.
Of course I wouldn't have any problem with a mod in the BSG universe or something using it, because in that universe it isn't established already. So that case would apply to most mods here, since they aren't in the WC universe.
Hell, IIRC Saga even used the example cloud background from the seamless skybox thread for BOTH of its atmospheric missions and nobody said "uuuhhh how lame, they use those generic clouds." (ok maybe somebody did but I couldn't care less). Those missions turned out pretty great.