Purely out of curiosity, I was posed the question with a hypothetical game corp. that has an online game that they require players to pay a monthly fee for. The specifics was that their service agreement stated that the user only has the rights to the client as long as their subscription is active.
However, said hypothetical SA poses a case where two players, let's call them John and Susan. John owns his own personal PC with the client installed. If John's subscription expired, by the SA, he would have to uninstall it essentially immediately. However, he does what any normal user would do and does not uninstall it. He is not licensed to run the client. However, Susan, assuming she has an active subscription, could run the client that resides on John's PC.
What if this client was under the GPL license? Would their monthly subscription expiring immediately deny their access to the source code of the application? (In terms of licensing, I'm not trying to somehow delete the code from their PC when their subscription expires)
Or, is this situation impossible due to it violating the license? (I can't remember where I heard it but I heard somewhere that subscription software is incompatible with the GPL but I haven't found any source on that.)