I think the key perspective here is that of “the average GitHub user who mostly ends up there in the process of attempting to fetch a library” (a.k.a. to use GitHub as the ecosystem-library package manager of last resort, for libraries nobody bothered to put into an actual package; or for special feature-branches or tracking bleeding-edge development.)
If such users will be more attracted to donating to developers via GitHub itself, than via other systems linked to through the GitHub README they land on, then donations will spike.
And if, at some point, this program becomes opt-out instead of opt-in, then these users might decide to donate to all sorts of people who never considered themselves “open-source developers” but who just happen to slap code up on the internet for free, mostly as a way of proving the provenance of the binary releases they make. For example, developers in the game-console homebrew community, or the Hackintosh driver community, might suddenly see financial support.
If such users will be more attracted to donating to developers via GitHub itself, than via other systems linked to through the GitHub README they land on, then donations will spike.
And if, at some point, this program becomes opt-out instead of opt-in, then these users might decide to donate to all sorts of people who never considered themselves “open-source developers” but who just happen to slap code up on the internet for free, mostly as a way of proving the provenance of the binary releases they make. For example, developers in the game-console homebrew community, or the Hackintosh driver community, might suddenly see financial support.