Okay, I have a question.
Let's say, I've copied 100 frames worth of ALAKTORN's input and used it in my movie. He says it's his private input, so he wouldn't like it to be copied, but rather, recreated. Okay.
Now what do we do to recreate it? Add 1 pressing of A on frame 50? It would still contain 99 frames of ALAKTORN's input. Add 50 random presses of random buttons at random places? We'll end up with still having 50 frames of ALAKTORN's private input. If we keep eliminating his private input further, we end up getting a desync, or suboptimal input. Even though, it still would contain some frames with ALAKTORN's input.
See, once you have copied something, you can't honestly recreate it anymore, since you already know what it was. And you can't eliminate the original input's trace, since it will break the speed record.
Going by the little I know of IP law, ALAKTORN would still own that sequence of inputs even if you changed all 100 of them, simply because you started with his work as a base. On the other hand, if you started from scratch and ended up with an exact copy of his inputs just because it's the best either of you can do, he'd have no claim to it.
This also answers Invariel's question about pressing start on frame 8: Everyone can hit it on frame 8 as long as they do their own work to determine that it's the soonest you can do so.
It seems a little odd, but my understanding is that the important part is how you got there, not the actual result you got. And no, I don't know how you're supposed to prove that someone copied your inputs if they're claiming they did it on their own.
That said, I'm not saying everyone needs to start from scratch instead of building on other people's work. People are perfectly able to either allow other people to copy their work freely or be added as co-authors, and you can (or so I assume) copy a cool trick without copy/pasting the exact input that was used to accomplish it.
Take this with a grain of salt though - I am neither a lawyer or a TASer. I just like watching these videos.