Just a head's up for anyone running Opensim dev master branch...
It seems that something has been changed recently in the development branch that has broken anything that rezzes/uses NPCs. The version I tested was OpenSim 0.9.0.0 Dev 7831d21 committed 2015-12-27 running with ubOde phsics. Any time a NPC is rezzed it immediately starts to drift toward the edge of the region where it gets stuck. It ignore sit commands but it will respond to a kill command, so you are able to get rid of it.
This change breaks my Clubmaster danceball (for NPC couples), my rez & pose utility, and anything else that rezzes NPCs.
Just thought you might like to be aware of that if you were considering updating a region to use it.
After some investigation, the issue appears to be tied to the new way that 0.9 handles access permissions. If the region and parcel are both set to allow full public access NPCs should still work. Anything other than that (group access or UUID-restricted access) will likely break them.