The base server product is free software, distributed under the GPL. If you want to stream content to your customers using unemcumbered royalty-free media formats (for example, Ogg/Vorbis and Ogg/Theora), you can easily do so without having to take out any license or support contract with us.
On the other hand, if you do license the Advanced Streaming Server, you get the additional features of our commercial server version. This includes professional GUI administration tools, access to proprietary formats for streaming such as MPEG, and access to our direct support system.