RIOTOUS versions before 0.3 only used VB.net as the server language for reasons of simplicity. However, due to the inclusion of basic encryption Python is now the default language for RIOTOUS servers. VB.net is still supported but only for servers that do not utilise encryption.
The machine requirements for a RIOTOUS server are hard to determine as RIOTOUS requires very few resources. From current testing a RIOTOUS server will run on a Raspberry Pi 3 Model B with no issues (Python), and a Windows 7 PC (VB.net).