[rbgrn]

You can add every feature zoints had without fear of patent issue, because I'm positive they have not filed any patents on those features and if they had tried, they probably would have never been approved by the USPTO!

You just can't use the name "zoints," as that would violate a trademark if they have it used as a legal entity or website name.

I'm no lawyer but this how I understand it.

Anyway, having backward compatibility is make-or-break for me. I simply can't switch to any other system that can't support my old URLs or I will lose so much traffic I'll be out of business. I'd make that one thing a top priority because it will give people a migration path to your system.