People used to buy TCP/IP stacks. People used to buy basic backup software. People used to buy fonts. At least nominally, people paid for browsers...When you come into the world of software you know that if you are up at a higher level and you have something superimportant, it's going to move down, down, down and eventually be part of every copy of the operating system if it is something superimportant.My first job in the software industry was with a company from which people used to buy fonts. That company pretty much died when Windows 3.1 arrived, which included TrueType technology.
Our crosstown buddies, Stac Electronics, also made software that Microsoft plagiarized (remember DoubleSpace?). Stac ended up suing Microsoft, getting an injuction on the sale of DOS until a settlement was reached.