That's not open source. The term "open source" (in the context of computer software) refers to a specific set of criteria (with some disagreement on philosophy and minor details[1][2][3]) that include the right to modify, redistribute and to use for any purpose. The term originates from the open source movement which branched off from the free software movement.

If open source meant simply that the source code is available, Windows would also have to be considered open source, as Microsoft makes the code available to some of its customers. This is not how the term is generally understood.

[1] https://www.gnu.org/philosophy/free-sw

[2] https://opensource.org/docs/definition.html

[3] https://www.debian.org/intro/free

ok, not closed, but restricted use. I think Microsoft should do (or buy Duende) their own platform. I've swapped to using keycloak, which is really nice, but it's a whole different world than .net