The use of ArchiCAD via an ASP set-up is a very rare thing indeed. When I first started looking into this I was told the only instances of this kind of set-up were in Sweden.

I was then surprised to learn that I had a client using ArchiCAD this way. They started with version 6.5 and that worked fine in the Citrix environment. Thigs went differently when they upgraded to 8.1.

You should confirm the following with your ArchiCAD support provider, but I believe this does work natively in ArchiCAD 9. I have a client using ArchiCAD 8.1 licenses distributed via an ASP using Citrix. We had to arrange for a special key from Graphisoft, but I recall being told that the customization wouldn't be necessary with 9.

If you have any questions e-mail me via PM