Gluu isn't based on OpenAM. Gluu is based on a whole bunch of other products (like Shibboleth) but not OpenAM. OpenAM originated from Sun's OpenSSO when Oracle bought Sun and FrogeRock was created. Incidentally this is the same time Gluu was created.

OpenAM is also no longer opensource. The source was closed by Forgerock in the beginning of 2018.

One of the forks that sprung from this source closing is wren:security ( https://wrensecurity.org ). Disclosure: I work on that project ;-)