Here is the view on this issue of one (non patent; copyright and
trademark only) attorney:
Compuserve seems to be passing along the GIF format license strictly
as a third party in order to avoid being sued by Unisys. Thus,
Compuserve's license agreement to its users alone has little bearing
on the validity of Unisys's underlying intellectual property rights in
the GIF format.
If Unisys delayed enforcement action unnecessarily, any party who is
sued either by Unisys or Compuserve probably would be able to raise
the defense of laches, an equitable doctrine that prevents a party
from benefiting from its own delay in enforcing its legal rights.
Fair use may also be a defense.
AOL and other users potentially may have such a defense--if Unisys's
delay in enforcement caused GIF to become a de facto standard, Unisys
may be estopped from any enforcement of exclusive ownership.
William F. Swiggart, Attorney at Law (Bitstream Inc.)