In the not too distant past, there was a school of thought that a covenant not to sue (CNTS) had a different legal effect than a patent license in the US.   Differences I frequently heard included a CNTS does not run with the patent, a CNTS does not exhaust the grantor’s rights, there is different treatment in bankruptcy under 365(n), and rights to pending patent applications cannot be granted under a CNTS.  Court have recently ruled on each of these points that a CNTS is no different than a license.

These recent decisions have shed so much light on the subject that, the next time you hear someone say there are differences, you may want to respond just by saying “quack, quack.”