Is there a good opensource service/subscription manager engine that contains things like service dependencies (i.e. if I choose service A, I also need Service B and Service C), subscription types, start and termination etc...
I'm building a site that sells various services and subscriptions and would prefer not to have to write that code as I'm pretty sure it's been done many times over (e.g. in e-commerce sw), but I'd prefer a small library / egine instead of having to integrate with an e-shop.