I looked pretty thoroughly on the GNU site but did not find anything specifically about NDAs. These two might help:
http://slashdot.org/article.pl?sid=00/18/1833229&mode=thread Dealing with the NDA question in job interviews
http://slashdot.org.article.pl?sid=00/05/15/2357243&mode=thread Compromises between companies and hackers re: NDAs
Hope this helps.
Janet Casey Free Software Foundation http://www.gnu.org jcasey@gnu.org