Well, it is an open source (GPL) engine, so there are no fundamental restrictions to use it in a commercial product.
If you were to make modifications to the engine source code, though, GPL obligates you to release the modified sources as open source under the same license.
Naturally you would need the rights to all the included content (WADs, textures, music, etc.) so for example basing it off, say, Doom II would not be possible without a license from id Software.
What this boils down to is that you can sell content and Doomsday add-ons you or your team has produced, but the engine and id/Raven game plugins source must remain free and open sourced, and you can't incorporate any of their content.
So, I'm also interested in making a commercial game for this engine. I think I'm clear about all the art/music/level/etc stuffs, but the code stuff is not so clear to me.
If I change how the gameplay works with only DEDs, and use the Doom game plugin without any changes in it, that's ok?
Or if I want new actions/etc for things, could I still use the basic movement/collision checking routines, or would I need to write them entirely new?
If I change how the gameplay works with only DEDs, and use the Doom game plugin without any changes in it, that's ok?
Yes. What you'd have there is essentially a commercial PWAD that is dependent on the original game content. As long as you only distribute your own content you'd be fine with such a set up. Ideally though, you'd probably not want your game to be dependent on that content because this would limit the commerciality.
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If you were to make modifications to the engine source code, though, GPL obligates you to release the modified sources as open source under the same license.
Naturally you would need the rights to all the included content (WADs, textures, music, etc.) so for example basing it off, say, Doom II would not be possible without a license from id Software.
What this boils down to is that you can sell content and Doomsday add-ons you or your team has produced, but the engine and id/Raven game plugins source must remain free and open sourced, and you can't incorporate any of their content.
If I change how the gameplay works with only DEDs, and use the Doom game plugin without any changes in it, that's ok?
Or if I want new actions/etc for things, could I still use the basic movement/collision checking routines, or would I need to write them entirely new?