"do i have to pay royalties on my own thoughts after that if i accidentally think in that language?"

An interesting thought, but we're not talking about human language systems here, right? To what extent does anybody think in a computer language? Rather, these potentially-copyrighted languages are used solely in application, correct?

This is not to say that I support the idea of copyrighting XML, I definitely do not, however, I do think that it's important to differentiate what people are and are not attempting to claim ownership over.

A more applicable case might be Fox's attempt to sue Al Franken over the use of "Fair and Balanced" - in essence attempting to copyright words in common use. Of course, Fox's suit was thrown out, but it addresses the issue of copywriting something that you did not invent, and issue that is also extremely frightenting within the context of patented genomes and companies holding copyright to the building blocks of life.