I don't recall that I ever did this with a FoxPro app. I used to make part of my money porting or cloning bespoke small business apps to OpenOffice Basic or OpenOffice with its Python integration. Visual Basic, QuickBasic, MS Basic PDS, TurboBasic, MS Access, and Turbo Pascal apps I'd replace with the integrated languages of the office suite.

Some of those originals used DBase III or DBase IV libraries. Some used bdb libraries. An awful lot used fixed-width fields designed into the application itself. Many of them I wouldn't have the source for, so I'd have to reverse engineer the data file format a little and then write a proper schema for a real database.

Sometimes the hardest part was getting the forms to look acceptable to employees at my client who were used to a curses style interface.