We recently began the process of moving one of our clients from a Server 2003 terminal server environment to a Server 2008 terminal server environment to take advantage of some of the new features including Session Broker.  One of the softwares that they use, Permco (a parts catalog software) was not developed for Windows Vista or Server 2008, and when activated was only activated for administrators on the machine.  Using a registry change logger, I was able to find that when activating the software, it was changing the following key:

HKEY_LOCAL_MACHINESoftwareWow6432NodeMDI

After granting Domain Users full access to this key, the program could be run by all users and activation was no longer an issue.