[_b8r0]

1. Set DNS to OpenDNS with porn filter on.

2. Watch for attempts to change DNS, then change back.

Not perfect (nothing will be) but should be good enough.

Bear in mind that ultimately if he wants to, he can uninstall the product, get his porn on and put it back on. Maybe charge per install activation?

Having said that, it doesn't sound like his problems are going to be solved by technical measures.