Hi,
"The popularity of Flash has been a big problem for our community, and we've been urging people not to use Flash for anything. However, we've just about solved that problem and we're soon going to release a version of Gnash which can even handle YouTube."
RMS http://www.groklaw.net/article.php?story=20070403114157109
GNU Flash player daily snapshots (source) are available from http://gnashdev.org/dev_snapshots/
Its good to see gnash coming along nicely. It plays most of the flash movies on the net including youtube (BEWARE: it is very slow) movies. Well you will definitely find movies which does not work as well as support for newer versions are getting added.
You will need to have quite a lot of dependencies to build it from source, but the configure script is so helpful it will tell you which package to install !! like apt-get install or yum package names. Also gives a nice summary at the end of configure. I think we should fix all the configure scripts to behave like this.
The developers are pretty helpful and the list is pretty active.
Happy Hacking Praveen