It's in part patents. My understanding is that btrfs does not get around them. This is not a vague patent threat, because there was an actual lawsuit with pate

It's in part patents. My understanding is that btrfs does not get around them. This is not a vague patent threat, because there was an actual lawsuit with patent numbers spelled out, namely NetApp v. Sun. You can check expiration date of those patents. More here: http://en.swpat.org/wiki/NetApp%27s_filesystem_patents http://en.swpat.org/wiki/NetApp%27s_filesystem_patents