Canola2 uses mplayer for playing Flash videos. You can throw a URL with a FLV video directly at mplayer, too.

mplayer and thus Canola2 don't play any flash. Flash video is not flash. It's a video container like AVI or WMV that was designed for being loaded by flash applications (such as the player flash app on YouTube). Canola2 simply parses the YouTube web page to find the direct of URL of the video file to play it via mplayer. YouTube is trying to hide this direct video URL from the user (you shall not download).