There are varying extents for ulysses pacts that can be taken as a project owner, though.

Tuxedo screwed themselves silly by taking too strong of a pact with their drivers, for example. Instead of going all the way with a CLA that effectively transfers copyrights to the project owner, you could go for a DCO under a less-restrictive, but still copyleft, license. For example, on an AGPLv3-only project, the DCO would require contributors to state their contributions are under GPLv2+ or maybe LGPLv2.1+.