Nadia,
I don't think details matter in this case. I suggested a way to compile new versions of PRG/APP while the current version is in use. You are free to use it or not.

Some functions in GPLIB (including who has a file in use) require "operator" rights. You can go around this by having a separate computer, logged on with the required rights - we call it a proxy server. On the proxy server runs an application, on a timer, that reads requests from a file, runs the appropiate function and writes the return values back to the file.
User applications write requests to the file and read the answer from the same file.