The idea that licensing is a hurdle for Linus is a myth. Linus has a signed-off policy that requires all authors of code submissions to provide signed-off. In the case of ZFSOnLinux, this includes Oracle, myself and others. That policy is the only hurdle:
Originally Posted by uid313
On that note, kernel updates are infrequent and vendors rarely backport filesystem changes. Users rarely update in-tree kernel components even when out-of-tree updates are available (e.g. KVM). This means that putting code into Linus' tree will expose future users to bugs that have long since been fixed unless the code itself was provably correct at the time of submission. With this in mind, I am not certain that I could provide my signed-off to Linus in good conscience should the opportunity arise. Providing signed-off to Linus would be to participate in the condemnation of future users to bugs that could have been avoided. I find the current situation where various package managers manage the installation of ZFS and its updates to be preferable. It ensures that users receive updates in a timely manner and protects users from being exposed to bugs in ancient code.
By making a contribution to this project, I certify that:
(a) The contribution was created in whole or in part by me and I
have the right to submit it under the open source license
indicated in the file; or