I believe vyatta is their base.
There's also this conversation regarding Ubiquiti's GPL issues from the past:
https://news.ycombinator.com/item?id=9331512
I've for three ERL's (one at home, two elsewhere) and they've been great so far. But I run their firmware, not OpenBSD, so I can't comment about it much. I also use their APs and I'm thinking of getting their IP cameras.
Indeed, Brocade closed sourced the main product in 2012 and left the community edition to die.
Thankfully the Vyatta core was forked in 2013 (renamed VyOS) and is under active development as a free open source project. [1]