Serendipity --
The issue is that SL is planning to over Havok pathfinding to third party viewer devs -- but only as long as the viewers can only be used to access Second Life. Which I can understand -- it costs money to license Havok code, and why should Linden Lab subsidize competing grids? If other grids want Havok, they can go license it themselves.
So. Assuming that other grids are NOT about to license Havok, viewer developers have to make a choice -- do they make an OpenSim-friendly viewer and ignore Second Life, where most of their users are? Do they say "no, thank you" to the cool new Havok pathfinding and keep going the way they are? Or do they grab the Havok pathfinding goodness and forget the crazy open source fanatics over at OpenSim?
Firestorm devs decided to be nice to everybody, and have a viewer with Havok pathfinding for the Second Life masses, and a version without the Havok pathfinding code for OpenSim.
Which is very nice of them.
You can read more about this issue here: