I am quite sure what you want to do will fell under the term "reverse engineering" and "interoperability" See this site and serch for interoperability http://www.chillingeffects.org/reverse/faq.cgi#QID193. In short you are allowed to do want want to do.Would it be legal to sell a product that interfaces to proprietary hardware (scientific instruments etc)?
The connector I am trying to interface to is listed in the manual as being 'proprietary' (not in connector type, just non standard in pinout).
by Jake Hertz
by Duane Benson