In later versions like BETA, are you gonna make it cost money or is is gonna be free? (If it is gonna cost money I think you should make a free version. :)
An easy 3D desktop Game Engine scriptable in Python. · By
It's free and I think it will always have a free version (even if I release a paid PRO version)!
If you want to support it's development, you can do it so by joining my patreon.
No, Cave engine doesn't require you to give any royalties from your game. It's your money so don't worry about that. Check the EULA if you have any questions about it: https://unidaystudio.github.io/CaveEngine-Docs/Docs/eula/