Re: DBase IV 'databases' (use this term as loosely as possible)
It was out of date in the 1980s. Well DBase 3 was.
The better products from mainly Nantucket and also a bit Fox.
I used Clipper (Nantucket) for years, later on Client Server, and yes there is recent software out there still compatible. Clipper was a PCode compiler but introduced lots of features into the XBase world.
Fox never hit the same heights. But its main legacy is DBF CDX FPT file format.
XBase is only dying now as the programmers retire and .NET programmers appear to be filling the gap.
Comparing Dbase to say Visual Objects would be weird but they are the same code family (VO was from the same team as Clipper).
So it is possible to take an old database and make it run client server with no data changes. And with the right compiler even compile the old code into a WIN32 console proggy.