"Custom Software" joke

My old boss had spent some time writing software packages for this particular program. The software usually came as source code and was executed through an
interpreter. He started a small business selling his custom software.
One day at a scientific meeting, he noticed another company was showing the software
with' remarkably' similar functionality as his own. He wandered over to watch the demo and the longer he watched, the more familiar it looked.
Eventually, when the sales gerbil had gathered a good crowd, he asked in a rather loud voice, “Are you using my copyrighted copy for this? ”
“Of course not! ” the sales gerbil replied.
“So, what happens if you press [key combination]? ”
“Nothing. ”
“Well, humor me. Do it for me. ”
“Ok, sir, but I can assure it you does. . . ” and upon pressing the keys. . .
the large screen popped up my boss' copyright notice.
It was widely accepted as the biggest laugh of the show.