Actually, others are claiming that X/Open is misusing a 'trademark' as a certification mark.

The USTPO has a special class of marks called 'certification marks.' This class of marks are used for certifications, not trademarks, per se.

There is a company called INUX that is challenging X/Open on this and other points:

www.inux.com

See this link at USPTO:

http://tarr.uspto.gov/servlet/tarr?r...entry=75680034

For more on certification marks, see this link:

http://www.patent.gov.uk/tm/howtoapply/certmark.htm