I just looked this up. According to Wikipedia, Gates called MITS and offered to demonstrate an implementation of Altair BASIC in roughly 8 weeks. He used those

I just looked this up. According to Wikipedia, Gates called MITS and offered to demonstrate an implementation of Altair BASIC in roughly 8 weeks. He used those 8 weeks to implement it. So I was wrong - he didn't license it, but merely scheduled a demo, before it existed.