I hope these guys don't flip like Gracenote did...Gracenote was all crowdsourced user contributions (for a long time at least) but then they closed off the data and sold it to Sony for $250+ million.
It would be completely against the spirit of the project to close in on itself, and as Leo_Verto mentioned, also pretty hard. With the core data available as CC0 and all the source code needed to run the servers, anyone could legally take all the data and set up a "LibreMusicBrainz" in some hours in the unlikely event that the MetaBrainz Foundation (the organisation created to support MusicBrainz and the other *Brainz projects) should ever flip.
All MB data is licensed as either CC0 (for core data) or CC BY-NC-SA for user-related data. [1]
As far as I understand it, this can't be changed unless every user who ever edited data agreed to that.
