Hi Miquel,

Yes, technically speaking you will be able to use it on all your ArchiCAD licences coming from that dongle (you have to serialize the add-on on any client computer by using the same unlock code).
Of course, as you understood, if you buy just one ArchiTerra licence you can use it only one copy at a time.

When you buy one of our product you got always the latest compatibility with ArchiCAD that means that if you buy one product now (today!) you will get a Registration ID that let you use the product under ArchiCAD 11 (the lastest ArchiCAD version) and older version.

Friendly
Fabrizio