The documentation is the first place to go to have in-depth informations about Itzï.
The Itzï community can help fellow users with the usage of the software. Just join the Google group there: https://groups.google.com/forum/#!forum/itzi
Additionally, you can follow Itzï on Twitter with the handle @ItziModel.
If you want more informations on how to use GRASS GIS, please refer to its documentation and user mailing list.
We do not provide any official or commercial support for Itzï.