Please see the most recent updates in the "Where did the .com name go?" thread. Posts number 16 and 17.
If he can’t be contacted then I would consider it an abandoned product. As long as it’s respectfully handled and he is credited with the original work, I’d not consider it an infringement. Just my thoughts as a developer.I just did an extensive online search for Glenn Duncan's uploads and from 2005 to 2011 he only has that email listed so I guess its go with the we tried and no way to contact him. He already shared it with all of us at AVSIM and it HAS been 17 years since it was uploaded for the old FS9 sim. IMO if he was able to be asked I have had responses from developers I contacted that were thrilled that some new life was given to their efforts.