For your information, there's no need for ClipDown (nor even GetVideo, if you use Youtube.js extension/userscript) if you use OWB (the MUI version).
You just need to configure OWB contextmenu entries to call Getvideo, that will itself call MPlayer (it's explained in GetVideo's readme).
And if you don't want to use GetVideo, just get
http://fabportnawak.free.fr/owb/scripts/YouTube.js and add it through menu ->windows -> userscripts in OWB.
Once done, when loading a youtube page, the extension will add direct links (for each found format) below the video area. On MorphOS, it would also replace Flash with HTML5 video and play it directly. On OS4, since there's no builtin HTML5 player, you can still configure OWB mimetypes (video/mp4 video/webm video/x-flv in this case) and tell it to call MPlayer when clicking this kind of file.
