Adobe Flash Media Server
Streams H.264 or VP6 (in an FLV or MP4 container) to Adobe's Flash Player using RTMP. Adobe Flash Media Server is proprietary and costs $995+ depending on the version.
It is most likely that in order to implement authentication/authorization we will need to develop our own application to run on the FMS. This shouldn't be too hard but it would require FMS Interactive or Enterprise edition. An institutional infrastructure that already runs FMS would need to allow us to deploy our own application. A FMS application is written in Actionscript and uses an xml file for configuration. See http://www.adobe.com/content/dam/Adobe/en/devnet/flashmediaserver/pdfs/protecting_video_fms.pdf for examples of how to implement authentication in a FMS application.
Wowza Media Server
Streams H.264, VP6, Sorenson using RTMP, RTP/RTSP, and Live HTTP Streaming. Wowza Media Server is proprietary and costs $995.
Wowza has some authentication add-on packages for authentication: http://www.wowzamedia.com/forums/content.php?115
If these default packages do not meet our need it should be possible to write our own extensions using their API. See the following for an example: http://www.wowzamedia.com/forums/content.php?137-Override-play-command-to-control-access-to-content
An open source flash server. It can stream FLV, MP3, F4V, MP4, AAC, and M4A using RTMP/RTMPS.
Similar to FMS, Red5 acts as an application server so we will probably need to write a simple Red5 application in Java in order to meet our authentication/authorization needs. There is some documentation on how to implement security through a Java interface as well as mention of a default authentication plugin provided in the 0.9 release.
A good post on how to do authorization in an application : http://stackoverflow.com/questions/1702729/red5-security-tutorial
Streams H.263, H.264, MP4, VC1, Flash Video, and RealVideo using RTP/RTSP, RTMP, Live HTTP Streaming, and MMS. Streams Helix Server is proprietary and costs $1000+.
Helix can do authentication/authorization but requires an additional licensed plugin (Helix Security Manager). There are not any API hooks that I could find.
Darwin Streaming Server
Streams H.264, MP4, and 3GP using RTP/RTSP. Darwin Streaming Server is open source but appears to be inactive.
Flumotion Streaming Server
Streams VP8, Ogg Theora, Flash?, and Windows Media? using ???. Flumotion Streaming Server is open source and built on top of GStreamer and Twisted with the option of buying an enhanced version.