I would like to know if I can use Quake1 or Quake2 engines to in my commercial projects? The source code of Q1 and Q2 was released under GPL. How GPL limits commercial use of that engines? What can I do and what I can't? In other words - should I pay for license to iD Software or how it works with that particular engines? Thank you!

You can do whatever you want as long as you include the source code, under the GPL terms.
Or you can pay 10K USD and have a non GPL license for it.

they'll let you negotiate a price for it as well....
id isn't that greedy. (well to indies, that is)

Quote: Original post by Alpha_ProgDes
they'll let you negotiate a price for it as well....
id isn't that greedy. (well to indies, that is)

Like I was saying, the price is 10K USD. Which is not bad at all.

Thanks guys. After paying 10k for non-GPL license, do I have to pay royalties to iD??

Quote: Original post by motorsep
Thanks guys. After paying 10k for non-GPL license, do I have to pay royalties to iD??

no.

Caveat:
IIRC: That license is for a single title. IE: you cant buy the license once and make 3 games with it, you'd have to purchase 3 times.