Is it allowed to make commercial game from this engine?

[MateOhoi]

I ask if its allowed to make a commercial game using the source from this engine/port?

The source code from the game (and probably a compiled version of this source code) would be made publicly available, and the art assets would be made from start, meaning no Quake art assets would be used.

HOWEVER the art assets required to play the game properly would be sold for a price (together with a compiled version of the game), and these art assets would not be made publicly available.

Is that allowed?

[skalleAnka]

It should be possible with the GPL. See here what John Carmack himself had to say about this when he released the original Quake code: https://github.com/id-Software/Quake

The primary intent of this release is for entertainment and educational
purposes, but the GPL does allow commercial exploitation if you obey the
full license. If you want to do something commercial and you just can't bear
to have your source changes released, we could still negotiate a separate
license agreement (for $$$), but I would encourage you to just live with the
GPL.

All of the Quake data files remain copyrighted and licensed under the
original terms, so you cannot redistribute data from the original game, but if
you do a true total conversion, you can create a standalone game based on
this code.