xemacs contributions policy?

XEmacs and FSF `Points of View' in <URL:http://www.xemacs.org/About/XEmacsVsGNUemacs.html> talk about entirely different things. `XEmacs' section is concerned mainly with technical issues, with lack of organizational ones, while `FSF' section consists entirely of organization issues. In particular, there is really lack of information about legal issues concerned with contributing to free software projects. FSF states legal formalities that are required in this case in <URL:ftp://ftp.gnu.org/pub/gnu/GNUinfo/standards.texi> and on <URL:http://www.gnu.org>. For XEmacs project one can not get similar policy information just as easily. <URL:http://www.xemacs.org/Develop/index.html> just invites to `submit patches to the mailing lists. The main question is: if one wishes to `make a nontrivial contribution' to XEmacs, what legal formalities are required from him according to XEmacs project policy? Perhaps the policy is requiring as little as possible, but I'd rather see this `little' stated explicitly.