SW3DFnx:

I'm using Ubuntu 11.04. I prefer to use the downloaded JNLP file because it automatically puts an icon on the desktop. After changing the permissions for the icon execution, I get a nice SH3D icon that launches the program after double-clicking. This works whether I'm online or offline. (I had to disconnect to test this, because I'm online 24/7)

The command "under" the icon is javaws "/home/hans/.netx/cache/http/www.sweethome3d.eu/SweetHome3D.jnlp" . Although it's different than your command, it's what SH3D (and Ubuntu?) automatically create.

Hans