Your own grid
Its possible to set up your own grid and if you want, use it behind your firewall. The Opensim software runs on both Windows and Linux. With a VPN connection you can meet and conference on your own operated islands behind the firewall.
You can find more on the Opensim software on this pages. Opensim.org
We do terraforming and construction of Islands and supply them in the oar file format. We also supply buildings and land files.
Some of them for free you can find more in the download section of the website.