We're running Foxpro concurrently with Clipper against some older Clipper DBFS. There's no problem so long as the Clipper App is using a CDX instead of NTX, and you SET CPDIALOG OFF in Foxpro, and finally, if the Clipper App is using the Clipper Descend() function in an Index, you'll have to re-write that index in Clipper, or Foxpro will choke on it.
(e.g., instead of Descend(Dtos(Date)), you have to come up with some god-awful thing like Str( 99999999 - Val(Dtos(Date()))) )