We do not include a Flash player because Flash itself was designed for MP3 audio files, not MP3 streams, and it handles streams poorly.
Because Flash itself is designed for individual MP3 files, it expects an MP3 to have a finite length and tries to load the entire MP3 file into memory. It does not know how to deal with the indefinite length of the MP3 audio provided by a streaming radio station.
The result is that, unless your Flash player disconnects and reconnects periodically (thereby interrupting the music on a regular basis, every 10-15 minutes) the Flash player will slowly consume all of the memory available on the listener's computer, eventually causing the browser (or operating system) to crash.
Neither of the above scenarios (frequent audio interruptions nor crashing the listener's browser) are suitable for a production stream, and thus we do not make any attempt to include nor officially support Flash players with Centova Cast.
There are a few Flash media players available which disconnect and reconnect to the stream on a regular basis (as described above) to keep Flash from consuming all memory on the listener's computer. One such player, the free MiniCaster Flash player, supports crossfading before and after the disconnection to reduce the impact of the audio interruption caused by these disconnections.
Centova Cast does offer a built-in integration option to work with MiniCaster. Due to licensing restrictions we cannot bundle MiniCaster with Centova Cast, but you can download MiniCaster here and enable it in Centova Cast simply by editing /home/centovacast/system/config.php and enabling the MINICASTER_SWF option. (The exact process is described in config.php itself.)
As you might expect, this still will not yield seamlessly uninterrupted audio, but in many cases the periodic interruptions are less noticeable with MiniCaster than with other similar Flash players.