52°North Iceland is a basic Java framework for OGC web services.
The 52°North Iceland was previously developed in the the 52°North SOS 4.x and was then extracted into an own project to be used in other projects.
The documentation is contained in the sources on GitHib as Markdown files. Advantage: versioned together with the code, close to the code, and text-based. Also suitable because iceland is for developers only.