Because it is open source, we can't stop anybody from forking it. We do however own the trademark to the name so you cannot use the name outside of the core community. We acquired that as part of Sun.

The issue though is of course not that cut and dry. The community would want to think over and debate any such move as it would have a long-term impact on the overall working relationship with Oracle, Sonatype, other Hudson contributors/sponsors, etc...