The XOOPS CMS is built on a framework that provides a set of specifications for:
The monxoops.fr site promised you, there will be available resources for developers.
To allow you to familiarize yourself with the kernel, here is a first element with the XOOPS APIs made available to the developer community. These documents have been generated thanks to Doxygen, a software documentation generator from source code and supported by Graphviz, a graph viewer.
Of course, this documentation is not complete since it was generated on the fly from the information contained in the XOOPS sources.