In the 90s, a startup called WebTV managed to negotiate and buy a perpetual SOURCE CODE license for Perforce (P4). WebTV built their own good version control sy

In the 90s, a startup called WebTV managed to negotiate and buy a perpetual SOURCE CODE license for Perforce (P4). WebTV built their own good version control system called "SourceDepot" on top of P4. When Microsoft bought WebTV they got this license, which enabled them to cheaply roll out P4/SourceDepot to massive teams for whom it was a big improvement over what they had been using. With access to the source, they could modify it to their needs and scale away. Google tried to buy a source license early on, but Perforce had learned their lesson from what happened with WebTV and wouldn't sell them one. That's how Google ended up doing elaborate projects for years to prop up and eventually replace P4. Source : I worked at WebTV, Microsoft and Google.