I think it is a perfectly valid question. If someone got sued by the holder of a patent and withdrew a piece of software or an application then that's proof positve.<p><a href="http://brej.org/yellow_star/letter.pdf" rel="nofollow">http://brej.org/yellow_star/letter.pdf</a><p>Would be a nice example, in <a href="http://brej.org/yellow_star/" rel="nofollow">http://brej.org/yellow_star/</a> there is a bit that says "There are instructions which are patented by MIPS and have been removed.".<p>That's a clear impediment to progress, once the MIPS instruction set was documented and people started to write software for it anybody ought to be free to re-implement these instructions for the express purpose of interpreting MIPS object code.