I have used that rgb to svid and composite adapter before. It is better than a neobitz that does the same thing. Worked great for me and the price isn't bad.
That ps/2 keyboard encoder thing is likely a piece of crap with all kinds of multpile key press issues.
Anything you buy from that guy will be covered in dust or dirt. I think he buries his wares in his back yard for safe storage.
He goes by yaton or y-plus on ebay.