>i'm not sure what you mean by "truly open-source"

Software distributed under a license approved by the OSI. These licenses, as far as I know, place no limitations on the type of speech that can be produced with licensed software. To use CryEngine, the people who work at CryTek must not find any of your project's content "objectionable".

>what "game engine options" are you referring to?

http://irrlicht.sourceforge.net/

http://www.ogre3d.org/

http://www.garagegames.com/products/torque-3d

https://github.com/id-Software

and many others; I'm sure there are big lists floating around. All of the engines listed here can be used even if the authors of the engine disagree with what you want to say, and I believe they've all been used in real, honest-to-goodness commercial games.

Unfortunately nothing in your list even comparable to UE and CryEngine. Ogre is just graphics engine (not game engine). idTech have great code, but it's even released dated and it's lack of tools.

Irrlicht and Torque is good options for small indie games (actually there many more great engines for small games), but they still can't be compared with "big" commercial engines.