[melony]

They don't have to fork anything, they can just add a built-in OAuth to ASP.NET Core Identity. They did that with JSON and created an in-house alternative to Newtonsoft's fast JSON library once it became popular enough. I didn't hear any PMs whining about "competing with the open source community" then.

[WorldMaker]

OAuth is too (stupidly) complicated for "just add a built-in OAuth to ASP.NET Core Identity". They had that in previous samples (which you can still find online if you look) and it was bad code that suffered from code rot and stopped being "OAuth compliant" especially with respect to even more (stupidly) complicated OIDC, so they looked for someone to maintain that and IdentityServer already existed and was OAuth compliant/audited. That's why it needs to be forked. Someone has to do the OAuth/OIDC hard work. Microsoft is paid to do that in other divisions of the company, of course, but it's all in Azure and they want you to pay for Azure AD alphabet soup that pays the bills for their OAuth/OIDC compatibility auditing.

> They did that with JSON and created an in-house alternative to Newtonsoft's fast JSON library once it became popular enough. I didn't hear any PMs whining about "competing with the open source community" then.

James Newton-King, the "Newton of Newtonsoft", was one of the developers involved in that project that decided a clean compatibility break with JSON.NET (which has been showing its age, but also has far too many users to easily break API compatibility) was necessary to achieve the performance goals that System.Text.Json was created to meet. That's not so much competition as it is cooperation.