In the 1970s, AT&T needed a lot of specialized, custom-written computer software to run its business. The company was forbidden to compete in the computer industry, so it could not sell this software. Instead, AT&T licensed its software and the related source code to universities for nominal sums. Universities saved money by using this software instead of commercial equivalents with pricey licenses, and university students got access to this nifty technology and could learn how everything worked. In return, AT&T got exposure, some pocket change, and a generation of computer scientists who had cut their teeth on AT&T technology. Everyone got something out of the deal.
The best-known software distributed under this plan was UNIX.