I would agree to a certain extent, but if there is a significant difference between the spin-off and the original (which should be quite easy to test, just compare the source code minus the comments), shouldn't some spin-offs have the 2 buttons too?

I think there should not be the hot list program that you cant use your Khan academy account. It waists time, and there should be a heart next to each projects so you can come back to it any time if there is  another tab called favorites and if you can follow people.

Khan academy is a great place to learn programming. Yes there is plagiarism, but this is a place for kids. It's not like they are getting money for a project.
The spin off button is a good idea. Otherwise, you'll have more kids copy and pasting without any link to the place they got it from.

So I'm a way, the spin off button prevents plagerisim .