If you're looking for a free MMO that has mainly samurais and ninjas, then there isn't any.
In Japan there is one with samurais and ninjas, but with a subscription fee. It's called Nobunaga's Ambition Online. The game is available for the PC and PS2 there.
As for an English/International version, I haven't read of any updated info on any web site so far (well, in English that is). If anyone else has more info, if this game will ever be released outside of Japan and in English, please share with us.
At Gamespot, the last update there was January 19, 2005. The article mentions the game possibly expanding to Hong Kong, Taiwan, and Macau.
There's also an IGN article dated February 1, 2006.
This post has been modified on2006-09-11-17:03:06by Hellefyr!