I wouldn't say it's unusual for SaaS offerings to be semi-opensource; the commercial vs opensource markets do diverge in needs and there is non zero risk in making >95% of your marketable advantage open source.
Regarding it's current, although waning, top choice for hosting open source software, I certainly do think we are starting to see the trade offs the open source community has been making.
There are tons of hosted GIT solutions. I've started using sourcehut [1] which seems like an rising platform that is also opensource. Hopefully youtube-dl ends up there instead of risking it on another big provider.
Not true. Github only hosts projects publicly for people who want to host their project publicly.
They don't have a mantra of all information wants to be free, and indeed their entire business model relies on hosting private repos.
I understand people wanting to host their open source on a server that's also open source. There's an argument it makes business sense if the closed source setup creates a long-term drift to GitLab or elsewhere. Nevertheless, I don't see the closed source as a contradiction.
You can love open source while producing a mix of open and closed source. Building a sustainable business often means being selective about it and seeing open source as a tool you can benefit from (enlightened self-interest), rather than an ideology you must adhere to at all times.
A hint of irony? It's freaking absurd. The "hub" for decentralized git (The "D" in DVCS stands for Distributed, doesn't it?) which has become the Kleenex of open source, is itself a closed, proprietary system. It's beyond ironic and well into oxymoronical. And then MS bought them! You can't make this stuff up.
Then your criticism should be levied at Linus for using an "overly" permissive license. You are allowed to profit off of GPL software. Investing 1000s of man years on a front end requires that people get paid somehow.
Which at the time of writing read as follows "It's not open source because the open source "community" is a liability and you want them far away from you at all times.
I'm not trying to be mean or sarcastic or anything. Just look at how maintainers are treated for a week and you'll see exactly what I mean."