The implicit contract of GitHub and the developer community is that they host open source projects for free, provide a feature-rich and professional interface, in exchange for developers to push their enterprise subscription at the developers' organizations.
This shouldn't be spelled out, I'm sure that GitHub knows better, but they are just playing the dumb card now and hope to nudge the community to accept this round of good will burning before they start the next.
The current list of anti-developer behaviors:
1. Code search requires login: https://github.blog/changelog/2023-06-07-code-search-now-req...
2. Ads are shown in the UI