The backbone of OpenATLAS is a Postgresql Database with the PostGIS extension. It offers a great performance and a high GIS-functionality. The OpenATLAS database can be stored on a server and be used in a multiuser-environment from an internal network or via an internet-connection. Alternatively you can also save all your data offline on your own disk and use a file-base Sqlite database with Spatialite. Both database systems are opensource and work on Win/Mac/Linux.
The interaction with the user happens via the graphical userinterface (GUI). There is one designed in MsAccess 2000, that has been in use for some years and for various projects. Currently we are developing a new and complete opensource Application in C++ (within the Qt framework) for Linux, Mac and Windows. The release of its first stable version is to be expected in early 2014.
You can connect nearly every common GIS program like Qgis, GRASS or ESRI's ArcGIS to OpenATLAS as long as it supports Postgres/PostGIS (sqlite/spatialite) or ODBC connections. For Qgis we are even planning to create a special plugin.
The Postgres database system also provides the possiblity to easily publish or display your data on the web, e.g within a WebGIS.