haha, I used this exact example in sales calls to make the case against app modernization. Sometimes, you just need the stuff to keep working, with $20-and-a-roll-of-duct-tape-level budgets.
My proposal was proxy layer sitting in between, running on something like k8s and written mostly by an LLM to provide a safe interface to queries against foxpro, with ratelimiting, query parsing, rest, whatever other business logic you want.
I am appalled at the fact it's still out there, but there is even older, more Archean stuff out there running literally the entire world :)