More seriously: Github is a business focused on turning open source community ethos into hard $$$. There is nothing wrong with that, and their model depends on people buying into the carefully constructed marketing of Github -hearts- open source. It's inconvenient for Github for people to point out that it is a closed source for-profit business with shareholders to please.

(One might even say that Gitlab is even more focused on turning open-source community ethos into hard $$$, because GitLab takes open-sourced community contributions to GitLab CE and rolls them directly into their paid, closed-source GitLab EE. Not that I'm suggesting that's necessarily a bad thing; I just want to make it clear that this isn't a Mozilla-style "take contributions from the community for the community's sake"-type thing.)

Just FYI, the GitLab EE source code is available at https://gitlab.com/gitlab-org/gitlab-ee/. You're right about the "paid" part, though.

SaaS companies are in a position where it can make it difficult for them to release their core software because it severely undercuts their viability if it's easy for people to set up their own installations.

What follows is naïve speculation as to counter arguments:

One could argue that they could differentiate themselves on better quality of service and support. It's possible, of course, but there may be enough people willing to put up with lesser quality that it may not be feasible for them to survive.

One could counter that taking advantage of community software contributions can lower their own internal development costs. Maybe, but there are very real costs when managing an open source project, including not being able to move as fast as they may want to. For example, if GitHub wanted to make a change for expediency' sake that wouldn't be appropriate for the community code, they're saddled with maintaining their own fork, which adds considerable overhead.

Of course GitHub loves open source. Their business is to provide a service that benefits open source (and closed source, for that matter) projects by providing infrastructure to manage their code. Some of their current and former employees are well-known in the open source community. I refuse to see anything nefarious or untoward (or even the slightest bit bad) about this until I see them doing something that impedes or actively works against open source. I see nothing "inconvenient" for GitHub about this. Some people are far too quick to go out of their way to look for hypocrisy.

(And as for "turning open source community ethos into hard $$$": my goodness. Yes, they make money. I hope plenty to continue to support the business, improve the service, and pay their employees well. How many community projects pay nothing for hosting on GitHub? How many devs pay to host their own projects, or fork others? The only reason I've considered paying was to host private repos: not open source. It'd be interesting to see their revenue numbers, but I suspect most of their revenue is for enterprise installs for software that isn't open source. Any corrections as to this most welcome.)

And there are alternatives for those who want open source. GitLab appears to be a great one.