Make even more explicit that this is the current and maintained version

People are regularly confused w.r.t. the state of the Uninett repo and this repo's state. Maybe an explicit statement helps.

README.md

@@ -4,6 +4,9 @@ mod_auth_mellon is an authentication module for Apache. It authenticates
 the user against a SAML 2.0 IdP, and grants access to directories
 depending on attributes received from the IdP.
 
+This module, under the `latchset` organization, is under active maintenance.
+It was forked from the original Uninett repository when Uninett chose to
+retire their version.
 
 ## Dependencies