Ventrilo was released back in 2002 and made available as a freeware for gamers to use for clan and social use. However the free service is very limited as you can only host an 8 person server. Rented server on the other hand can maintain up to 400 people at the same time.
Ventrilo only sells licenses to register hosting companies and business. You are unable to host anymore then 8 people on your own computer at home. This means that the only way to host a larger voice server is to rent a monthly server subscription from a company.
Despite looking very plain in design, Ventrilo is a very useful piece of software. It is more then enough to keep you your friends chatting online around the clock.