>I don't think this is correct. I seem to remember Fox Software working on the patent before it merged with Microsoft.

Yes, Fox Software had applied for a patent. It was pending when purchased by Microsoft. Some years later the patent was rejected; it depended on too much "prior art". The technique used is known and has been incorporated into other products. The copyright would apply to the code that produces VFP -- if another implementation is created in a clean room (meaning no reverse engineering) then it is not a violation of copyright.