I’m not concerned about the direction of development, I’m concerned about Oracle holding the (or at least a significant part of) copyright to some software which is used as a Linux module, but which is licensed under a license which is (arguably) incompatible with the GPL.

If Oracle wanted to, they could easily release their copyright under a dual license or something else to clear up the licensing issue. They have not, and have chosen to retain the ability to sue every Linux user using ZFS. This concerns me.