"All." It's explicitly not compatible with GPL, though. It has clauses that are more restrictive than GPL, and IIRC some people who contributed to the OpenZFS

"All." It's explicitly not compatible with GPL, though. It has clauses that are more restrictive than GPL, and IIRC some people who contributed to the OpenZFS project did so explicitly without allowing later CDDL license revisions, which removes Oracle's ability to say CDDL-2 or whatever is GPL-compatible. So even if someone rolled up dumptrucks of cash and convinced Oracle that everything was great, they don't have all the control needed to do that.