Sun received dozens if not hundreds of patents for techniques used in ZFS and since Oracle purchased Sun, it now has those patents. btrfs uses many of the ideas

Sun received dozens if not hundreds of patents for techniques used in ZFS and since Oracle purchased Sun, it now has those patents. btrfs uses many of the ideas that ZFS uses, so it is highly unlikely that btrfs does not infringe on at least some of those patents. People who use ZFS have a patent grant through the CDDL, but people who use btrfs have no such protection from the GPLv2. So far, I am not aware of anyone who has gotten any legally binding assurance from Oracle that shipping btrfs will not be a problem. I am also not aware of anyone in the btrfs community asking Oracle to do something about it. If btrfs takes off, the ZFS patent portofilo could ensure that Oracle is the only company that can legally distribute btrfs. Consequently, Oracle's legal department would likely be able to have a field day with any company distributing btrfs. In the meantime, their competition will have to develop workarounds and Oracle would be ahead because they will have a better filesystem than they would have had they been upfront about this issue. What Oracle might or might not do with the ZFS patent portfolio in the future is speculation, but the fact is that Oracle appears to have reserved the option to use it in future lawsuits.