If you use copilot and it generates a substantial amount of code, you don't know if that might be a replica of code from another project with an incompatible license. If you are law abiding and/or want to respect open aource licenses, then it is on you to figure out what if any license that code would fall under. Which means copilot would only be useful to developers who don't care about FOSS licenses or only use it for snippets that couldn't possibly be considered original enough to be covered by copyright.