The Reaver of Darkness, thank you for your remark. May I ask you to explain your point much more?
Ok, let other people do it. I cannot see the problem.
Exactly, I do not distribute the X-Com: Enemy Unknown. I distribute only my alterations.
Of course, people should have a licensed copy of the game.
I'm afraid I did not understand, but anyway I do not have any commercial plans.
Bottom line: "You can't put it under the GPL" - can you explain why not?
I already told you that no one here uses licences for his mods.
The reason for this was that working and distributing modified vanilla assets is juristically a grey area.
Meaning that if ever one of the current X-Com UFO Defense Licence holders (e.g. Firaxis) steps forward and forces us to remove content because we violate the original Licence of UFO Defense we are fucked.
Since we encourage to buy the original and it is mandatory to play either OpenXcom or possible Mods our modding activity here goes basically undisturbed.
And I for myself would like to keep it that way.
And you can not put already licensed content under a licence of your choice because you are not the owner of the intellectual property in question.
When you have no ownership, you have no right to licence.
EDIT:
As much as I like the GPL Licence and all the wonderful software the GNU project has so far produced and which I use myself daily, it is not applicable here.