This idea ("make a stronger license") has come up in previous discussions of Copilot as well[0].
The problem is that the Copilot project doesn't claim to be abiding by the license(s) of the ingested code. The reply to licensing concerns was that licensing doesn't apply to their use. So unfortunately they would just claim they could ignore your hypothetical Free³ license as well.
> The problem is that the Copilot project doesn't claim to be abiding by the license(s) of the ingested code. The reply to licensing concerns was that licensing doesn't apply to their use.
I think github is largely correct in their view on licenses. However I would argue that you could create a stronger legal binding than say a GPL-3 license. For instance you could require and enforce that anyone that wishes to read the repo must sign a legal contract or EULA: "By decrypting this git repo you are agreeing to the following licenses, restrictions, contractual obligations, ..."
The problem is that the Copilot project doesn't claim to be abiding by the license(s) of the ingested code. The reply to licensing concerns was that licensing doesn't apply to their use. So unfortunately they would just claim they could ignore your hypothetical Free³ license as well.
[0]: https://news.ycombinator.com/item?id=34277352