I actually maintain all rights to the core code ... as part of the agreement I'm hosting the application for the client, so they are technically subscribing to the application (first year is, of course, paid for, next year a small amount of money will exchange hands)

I'm inspecting now for other opportunities within the industry. This was fairly customized for a very specific need, so it still remains to be seen ... I also do not want to distract myself from my current startup, but I'll take the opportunity if it arises and I can manage it!