I did some contract work for a “gentleman” many years ago who was having difficulty getting the performance he needed out of a homegrown, poorly implemented 3D rendering engine created by developers who had never built a 3D rendering engine before.
I had developed, as a separate personal project, a 3D rendering engine that would fit the bill, solve many of the problems we were suffering.
He wanted me to hand over the 3D rendering engine for free, with a perpetual, exclusive license.
He pleaded, he threatened, he cajoled, he tried to reason endlessly with me that I should give him the source code “because I wasn’t using it.”
He attempted to reason that because I was not using it for anything at the time, that I had no right to attempt to charge him for all of the hours I had put in to the work beforehand.