No, you cannot add any restriction to asking for sources nor to redistribution. You can only ask in exchange for sources for the cost of physically distributin

No, you cannot add any restriction to asking for sources nor to redistribution. You can only ask in exchange for sources for the cost of physically distributing the source, nothing more, and in that case you must offer it to anyone asking at all, even if they do not have the binary. Otherwise, you have to distribute it for free on the same medium as the binary itself. You can not either add any restriction to the act of distributing the program or it's sources. The GPLv2 says for example "You may not impose any further restrictions on the recipients' exercise of the rights granted herein.". The question is whether or not terminating the subscription is a restriction, which it totally is to any reasonable reading by a layperson, and may be as well in front of a judge.