TBH this doesn't affect most of OSS - most OSS will fall well within the limits as set out - with the possible exception of the release limit of 7 if they have lots of different projects.
WRT JitPack, it's a non-starter inside a lot of larger companies who rely on the "security" of Maven Central and actually refuse to let engineering teams consume from anywhere else. Of course, at the same time, they are puling from NPM.. 😂
Arguably Maven is the hardest popular package manager to actually get publishing set up on (you need to own the domain), so any replacement would have to also meet that bar. I'd also be interested to see if the likes of JitPack will also take the opportunity to start monetising once they see that it's a viable alternative. I suspect that Sonatype starting to charge for consumption is also on the cards (and it's actually the wider source of abuse compared to publishing traffic)