Is/ought revisited

Here is a reputedly defensible version of the famous principle that you can't derive an 'ought' from an 'is', taken from a paper in defense of the principle that 'ought' implies 'can' (Peter B. M. Vranas, 2005) (this was linked by ephphatha in a previous post), although the link is now broken:

(I/O) No valid argument has a conclusion that is a singular* moral claim and premises that form a consistent set of nonmoral claims.

My question is, does the following example serve as a counter-example to I/O? (Also, if so, why? If not, why not?):

1) Jones believes that Smith ought to concede that we can derive an 'ought' from an 'is'.
2) Everything that Jones believes is true.
3) Smith ought to concede that we can derive an 'ought' from an 'is'. (from 1 and 2)

*singular moral claims are understood as moral claims expressed by asserting or denying that a specific agent S has (or does not have) a moral obligation to @.

Belief

What does it mean to say that somebody believes something?

I think that a belief is a mental state, representational in character, taking as its content something that could in principle be stated as a proposition. To believe p is to hold that p is true.

How can we distinguish between believing that we hold that p is true and actually holding it to be true? Beliefs predispose us to certain behaviours. If we consider what people actually do, we can sometimes discern a difference between what they profess, and what they actually believe.