[aurizon]

There are the dongle solutions, each unique and keyed, but has a cost. There are the 'phone home' solutions, but if your product is good and gets share = attracts hackers who figure it out. Game people fight a constant battle = steam servers, essentially a mandated phone home cloud. You can add a few backdoors with a mechanism that scatters them with many entry points that each send a 'canary in a coalmine' alert = you know, but nothing is hacked. Once known, the canary can be used as trigger for unpaid product. Not sure how legal that is, but there are people who create software security methods dongles, cloud servers, canaries etc - google that and ask and assess the cost/benefit ratio. Some just tolerate the problem and their only solution is an update gatekeeping method. Reasonable price is also a good plan for a large base = $$ in numbers...