Wikipedia
CastGate was an attempt from the ETRO-TELE research group at the Vrije Universiteit Brussel to break the chicken and egg problem of IP multicast adoption on the Internet.
Although multicast would have allowed an Internet user to receive rich media and other content without placing a high burden on the net, it was still unavailable to most Internet users. The CastGate project tried to fix this by allowing end users to connect through an automatically configured IP tunnel over networks which did not natively support IP multicast. The idea was that if more users have multicast capability, more content providers would see the benefit of streaming content over multicast. The hope was if enough content providers and users used this service, then more Internet service providers would enable IP multicast natively to their customers.
CastGate supplied a software client for both Microsoft Windows and Linux to connect to the CastGate tunnel network. It also supplied tools to add tunnel servers and tools to receive Session Announcement Protocol announcements from the multicast network with video and audio streams.
The project maintained a web site through 2007.