you have to own them because how else will you test them?
well what you could do is actually install the demo's of the games and your good to go. But then not many people know that lol
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also how else are you suppose to have a good selection of textures at your diposal if you don't use what already comes with the game... plus the fact the texture files are BLOODY huge, infact they are the bulk of these games.
To redistribute the first level in Quake your talking the better part of 5Mb on its own ... there are 4x 10 levels ... thats 40x5 which is 200mb!!
and each consecutive version only gets larger with more textures.
Tsu'va Oni Ni Jyuuko Fiori Sei Tau!
One block follows the suit ... the whole suit of blocks is the path ... what have you found?