§5.c of the GPL Version 3 states explicitly:
> You must license the entire work, as a whole, under this License to anyone who comes into possession of a copy. This License will therefore apply, along with any applicable section 7 additional terms, to the whole of the work, and all its parts, regardless of how they are packaged. This License gives no permission to license the work in any other way, but it does not invalidate such permission if you have separately received it.
As in, all modifications must be made available. Is that not meeting your definition of giving back? GPL (all variants) is one of the most widely distributed of the free software licenses and has an explicit "give back" clause as far as I can see it. -- and is part of why some people referred to GPL as a "cancer".
FWIW the issue I've come to have with copilot is that you're not explicitly permitted to use the suggestions for anything other than inspiration (as per their terms), there is no license given to use the code that is generated. You do so at your own risk.