>>As much as they'd like to make it illegal, reverse engineering is still legal.

Especially if the original vendor has deprecated and/or no longer supports the product in question. Plus, free distribution of runtime always was a product feature and VFP Compiler still requires a VFP development license. Meanwhile Chen has fixed the residual bugs left undone when MS finished with VFP. Example- anybody experienced the infuriating phantom breakpoints where you're tracing an app and it keeps breaking at the wrong place where there is no breakpoint? Bug existed for years to my knowledge, now fixed. Reporting bugs, anybody? Prg too long bug? All fixed.

I'd also observe that in most jurisdictions, you need a set number of key differences to avoid claim of copyright breach. Having said that a 64-bit version of VFP involved massive change, for numerous reasons apart from Copyright I'm not sure that any vendor would want to claim the opposite.