Yes. he is...
we can't refute what's written in Shincho Koki / Nobunaga Kōki. It's a legit document.
The thing is the word samurai has a LOT of derivatives depending on which person you asked it to.
BY DEFINTION.
Samurai = saburau = to serve(their lord).
did Yasuke serve Nobunaga?. Yes.
He got stipend, given a sword and even given a house to live.
Samurais are retainers of their lord.
Yasuke was permitted to carry weapons and his lord's weapons.
The Original requirements:
Horse Archer. ( because Horseback and Archery ain't exactly cheap, takes years and is only accessible if you're filthy rich and when you're filthy rich you automagically pass the requirements below. O-yoroi is a Horse Archer armor.)
the other requirements.
- Of noble blood. (this is bullshit, because we all know it's just political and military power)
- Follows a code of honor. ~BUSHIDO~
- Is a vassal. (meh... it's not really a requirement as being retainers and bodyguards are sufficient.)
If we asked Nobunaga now... Eccentric man as he is. Chances are he would say Yasuke is a samurai.
That's just how Nobunaga is, Great men do not follow the rules of other men.
Now comes the interesting part.
No story recorded after he was caught and his life spared. WHY?
methinks: he committed Sudoku after.
imagine.. you're a black guy, a servant of a white guy, went to japan, treated right! was even given education! failed to protect friends who acknowledge him. was not allowed to commit sudoku in Japan by his captors for being a "foreigner" and sent back to Jesuits, which I think was the absolute disgrace someone could give to Yasuke.
Yasuke is twice a samurai and twice a ronin.
served Nobunaga (samurai), Nobunaga dies. (ronin)
served Nobutada (samurai), Nobutada dies. (ronin)
Again, there are "standards" depending on who you ask. in practice, he is, in ideals, he might not.