FushionAuth, a free self hosted identity provider server
FusionAuth gives you quick and easy authentication for any type of application at all, including web, mobile, desktop and console apps. Use FusionAuth's OAuth, OpenID Connect or SAML v2 front-ends, or build your own login experience. We love developers, so if you build your own, our library of content is here to help you along the way.
This looks very interesting. The other strong similar alternative is https://www.keycloak.org/.