As you can read in FAQ11764, Avalanche only supports running a single instance of commander per PC or server.
A workaround anyway allows to run multiple instances of Avalanche on the same pc or windows server, but this has not been tested and is not recommended as it may lead to unexpected behavior. Create a shortcut of the exe before opening the commander, then add an extra parameter (-port xxxx) to the shortcut. User will have to provide a unique port number every time he wants to start a new Commander. This will work like pre-v4.00 release behaviour.