How would they be subsidizing competing grids at all as that viewer code would be useless in grids that did not have the Havok engine, right? I don't think the functionality in question in enabled by the viewer alone.
If the above is true then I don't see why it is in the interest of the Havok folks to have this restriction. If anything it would make it more likely that users of non-SL grids would be pushing their grids to use Havok and thus more likely lead to an increase in their business. I do see why it is in SL's interest to have this restriction however.
Hmm. I suppose the Havok folks could see it as more likely that alternate server side Havok-like support would be developed considering the availability of Havok capable viewers.
In practice how are viewers going to be restricted? Is there a clause that says that Havok supporting viewers cannot fall back to work otherwise on grids that do not have Havok? Or is it simply implicit in the nature of the code?
I do think the Firestorm devs are being very nice to everyone. And very wise from a business perspective.