Patents aren't necessarily the worst problem ahead for the poster.
Another, potentially bigger problem he may encounter is that (depending on his contractual relationship with his current "clients") he may not own the software - they may claim that it was a work for hire. There position will be that the software was created for them and they are the "owners".
In that case he doesn't just have to worry about the trolls he doesn't know...but also about the ones that have already paid him.
Not all work created by independent contractors are "works for hire", though, so he may not run afoul of this issue.