Forgotten Tale is currently in the Alpha-Stadium.
Here you can download the Alpha 3: Link
Currently, Forgotten Tale is (as well as the TowerEngine) available under the GNU General Public License version 3.
When it is finished, it will be available on Desura for buying.
There's a File Format for 3D-Meshes called "Tower Mesh" which was developed espacially for Forgotten Tale.
Also, there's an editor for that. Here you can see a couple of sceenshots (click to zoom):