But even if only 1% of ideas were copyrighted, that is still a tax on the use of all ideas. In a world without copyright, I can download any dataset at will and analyze and remix it to my heart's content, and share my findings. But in a world with copyright, if there was one "copyrighted" land mine in there I open myself up to financial ruin. So one must tread carefully when working with any external ideas.
If you as an end user want to modify the source code for your own use, then that is fine. If you want to distribute it, you must state the changes, and you must also do so for any code it is linked with. The original maintainers are then also free to incorporate said changes should they chose.
https://en.wikipedia.org/wiki/Debian_Free_Software_Guideline... http://people.debian.org/~bap/dfsg-faq.html
The problem posed with copilot is in fact the opposite. By taking it to its logical conclusion, this might make it possible to disregard this effort and use GPL code on your private project.