True - the tricky part in Rokugan is that while on the one hand, they say all new classes, feats, etc, are open content, they also claim everything adapted from Oriental Adventures is product identity. And since the Samurai and Shuwhatzit are "Adapated from OA", they might therefore be off limits.
But! If you read the definition of what "Product Identity" is, it doesn't include things like classes. Therefore, the Samurai and Shuwhatzit class cannot be considered product identity, since they aren't eligible to be PI.