> It is over-complicated, when all that needs to be done is exchange of two files between SP and IDP. Or there is too much free interpretation/implementation of SAML as protocol around?
SAML is not that finely defined protocol, and there are also a lot of vendor-specific nuances in actual implementations you can meet in real world deployments. Some of them even may implement parts of it in a way that doesn't conform to the specs.
Usually you don't need to delve that deep to add SAML SP to Gluu, most of the time it's done in one go through web UI. Sometimes it may need a bit of troubleshooting, logging monitoring, traffic capturing etc. But some SPs may be tricky to configure and may require direct edits to Shibboleth configuration files, intense discussions with their support etc.
>Maybe a collection of guides for configuring Gluu for different 3th party SP will help lot of people.
You can find several examples in the "Integration" section of [the doc portal](https://gluu.org/docs/).
>Other commercial IDPs makes this look so easy.
Gluu CE is offered under a bit different business model. We don't charge users for using the actual software, giving them an option to master all intricacies of configuring and managing it themselves, and only offer them a paid support assistance as an alternative. We also provide a decent amount of information via documentation and this support portal free of charge, in addition to other publicly accessible resources (protocol specs, Shibboleth/CAS/OpenDJ docs etc) which should cover almost all their needs. But we can't afford spending that much time on providing detailed guides on all possible integration scenarios like companies acting under fully-commercial business model do. That's just a different kind of offer.