Comes in binary form from Debian and Ubuntu. I can add it to any other distribution via DKMS. Same core ZFS code as BSD uses.
Honest question - if it comes in binary form, how can you know it's the same core ZFS code BSD uses?
Same as anything else installed as a binary package - you trust the people packaging/providing the binary. If you don't, build it yourself. The source is publicly available.
Or you build it yourself and verify you got the same checksum.