Tim Bray explains what actual interop between MS and Sun would look like. But then again, this alliance is all about Sun finally noticing that Linux thing eating their low end server market away, so why should MS care?

I guess it’s good that Steve and Scott made nice, and there’s no doubt that when the customers tell you to interoperate, then you bloody well interoperate, so it was a good piece of work (see Pat Patterson’s take in a comment on his own blog). But this glue for linking to Microsoft’s WS-Federation is a second-rate solution at best. Among other reasons, WS-Federation is yet another WS-backroom spec that might change (or go away) any time the people in the backroom want it to; not something I’d advise betting on. If you have products from any two vendors that implement Liberty Alliance specs properly, well, they interoperate.