What exactly do you mean by "open". The standards are encumbered by patents. And the Microvell deal is aimed at non paying users of M$ patents. Does Mono violate M$ patents?. To be sure u would have to higher a lawyer and do a patent search. And according to Miguel De Icaza he does not know of any possible violations. But of late he does not seem to know a lot more. Recently he tried justifying the OOXML ECMA standards. His argument was that there was nothing wrong with yet another standard. Which completely missed the point that OOXML was not a standard but an incorrect and incomplete description of a single implemetation of MSoffice blobs. A standard is one when it has more than one independent implementation for starters.
Not true. Anybody is free to make a "standard" of their own. Of course, what makes a standard "stand out" depends on how popular it is and how many implementations of it are out there.
There's only one proper implementation of an XHTML 1.1 based browser. It's still a standard, is it not?