It did not fit in 4K on the Apple ][. PET and Atari were also 6502, like Apple, so mostly the same code. Altair and the others were 8080. So, only two interpreters. It was the same design on two instruction sets, with some simple customization per vendor. Some had a Z-80, with extra instructions available: using those made your program smaller, but slower. It is doubtful he did.

That it was so short also meant there just wasn't much to it. Bill doesn't need your unpaid defense. He didn't make his $billions from BASIC. That just gave him a customer list.