Support for YouTube and Lulu.tv streaming video is a key feature of Gnash 0.8.0, the third alpha release of the open source Flash movie player. Gnash is available as a standalone application, or as a plugin for Firefox, Mozilla, Konqueror, and Opera.
According to the release announcement, "Gnash supports the majority of Flash opcodes up to SWF version 7, and a wide sampling of ActionScript classes for SWF version 8.5. All the core ones are implemented, and many of the newer ones work, but may be missing some of their methods. If the browser only displays a blank window, it is likely because of an unimplemented feature."
Developer Miriam Ruiz blogged a few tips about Gnash's dependencies:
We have packaged Gnash with the OpenGL backend this time, to be able to support Konqueror’s plugin. If you want to be able to watch YouTube or Lulu TV videos, don’t forget to add the recommended packages: gstreamer0.10-plugins-base, gstreamer0.10-alsa, gstreamer0.10-fluendo-mp3, gstreamer0.10-ffmpeg. If you’re not using ALSA, you might need to replace gstreamer0.10-alsa by the corresponding package providing gstreamer0.10-audiosink that suits your system. Without this packages, you will be able to reproduce Gnash films, but not to see video streams.
Ruiz also notes that this version "is still not modular," but that is planned for the next release.
Source for Gnash is available from the GNU Project FTP servers.