If the lawyer had said "Yes", he could have answered "No": Gates knows that patents don't really apply.
Otherwise the lawyer would have had to define it, which runs the clock down on how long Gates had to actually answer questions.
>If the lawyer had said "Yes", he could have answered "No":
No to what? The original question was whether Gates was indifferent to developer usage pure vs. proprietary APIs.
This was an attempt by the lawyer to color the APIs as proprietary while asking about pure Java vs. Microsoft's API functions and Gates wanted to know exactly he meant by that term before giving an answer to the question which could imply that was agreeing with the lawyer that the API was "proprietary", which could mean different things to different people.
It's like a lawyer asking "Do you like the brand of the beer you stole?",
The proper answer is "What do you mean, stole?".
Not, "No, I don't like Budweiser".