Those skins are not in fact BeOS clones, but Zeta clones, the new BeOS operating system.
Here is the first one i have made a couple of months ago, from the GUI of the beta media player
http://remi.grumeau.free.fr/BeOS/Zeta%20Champion.bsz
And here is the clone of the brand new Zeta MediaPlayer, official one from the R1 of Zeta:
http://remi.grumeau.free.fr/BeOS/ZetaMP.bsz
Enjoy :)