
As far as I know Clonk Rage comes with a freeware key today since it was released as freeware and I think this one should work with c4group as well. But without a keyfile, I'm not that up to date on the CR version of c4group, so I also don't know if there has been a c4group version released that doesn't require a key at all anymore. I just know the OpenClonk version of c4group does not require a key, but that one might not work for CR files.
EDIT: Sorry, didn't have in mind that CR was patched to work without a key and doesn't have a key anymore. See my post above in reply to B_E.