After downloading the code and playing around with it, I concluded that an obvious companion tool was missing. Swap the format used with the Bound List Program Information (QBNLPGMI) API from PGML0100 to PGML0200, make a few other minor adjustments, and in no time DSPSRVUSG is in the toolbox!
If your shop uses service programs, the DSPSRVUSG utility may be just what's needed to lighten the maintenance burden when it comes to finding out where that service program you just modified is used. The command also displays the signature assigned to each instance of the service program, which is invaluable information if you are one day plagued by a perplexing signature violation error.
In addition to the source for DSPSRVUSG, the updated code for the original DSPMODUSG tool is also included. The latter has been modified to use pointers to retrieve the list entries from the user space. Click here to download DSPSRVUSG and DSPMODUSG.