>I'm planning to enforce licensing through small, VFP-encrypted .APPs customized for each client. The main application calls the custom .APP and won't run without it.
>
>Will the built-in VFP "encryption" defeat attempts to modify custom strings in the .APP by products such as ReFox? Or, prevent ReFox reverse engineering the .APP and replacement by another?

No, it will not prevent ReFox from reverse compiling the application. All encryption does is scramble strings so they aren't readable.