Benchmarking forbidden?

I heard an allegation yesterday that you can't publish benchmarks on 
MSXML performance without explicit permission from Microsoft.  I poked 
around a bit with Google and found no evidence.  Somebody please tell me 
this isn't true.  If true, is there a pointer to restrictive language? 
Also if true, is it just them or are there XML-related components out 
there that have this kind of encumbrance?
-- 
Cheers, Tim Bray
         (ongoing fragmented essay: http://www.tbray.org/ongoing/)