>What are the implications of running FoxPro on a server, and allowing users
>to login to the server to do development?
>

You need to be running a Server that provides terminal Server type access - Windows terminal Server or Citrix.

>If you change a registry key for an ocx control to point to another folder,
>instead of the windows directory, what effect will it have on the windows
>server? Will it cause the server to stop responding?

No if it's done improperly, it will cause every process or thread that references the GUID or ProgID to use the new component, which can be disasterous if this is done while someone is using the shared copy of the COM component while you try to update. Both WTS and Citrix offer a mechanism for administrator equivalent users to install updated apps and system components safely.