You can run any executable - no matter in what language it is written in - by running/shellexecuting it or CreateProcess API function. And any language can run EXEcutables, because any language can use these or one of these Windows OS built in API functions to run something. In regard of "without exiting Foxpro", what should that mean? Any executable runs in it's own process. Within the same process you can only run code from DLLs, which can dynamically (at runtime) link to anything, and so run in the same process. That's also possible cross language. There always has been and will be the possibility to integrate things written in many programming languages, if there wouldn't be, there could only be one language, or each language would only run in it's own bubble.
What you can't do is write single programs in multiple languages, not within the same method, not within the same source project compiled by one compiler.
I don't know what thread you refer to with running vbscript with VFP, a link to that would help. Most probably you saw something running wscript, or automating office VBA. Of course, again this runs in a separate process.
There are EXEcutables, each one running in an own Process, there are DLLs, "linking" into already running processes dynamically, there is OLE/COM, which allows automation, a weaker link to both in the same process DLLs (inproc COM Servers) and other processes EXEs (out-of-proc COM Servers). You can create those COM Servers with VFP for use in other COM enabled languages, for example.
Then, besides these techniques, you can share data, of course, via shared memory or pipes or much simpler files and databases.
Interoperation is no magic and has many interfaces and possibilities. Even for no direct interoperability you can share data via files, databases, connect via http protocol to services and others.
All this is no limitation nor exclusive to VFP or VB or any language, but in the end it also means you don't run VB within VFP, you may have VB code you pass into wscript.exe, for example, but that makes wscript run that code.
Bye, Olaf.