This sounds to contemporary ears like archaic English.
The usual way of expressing this would be
and if I dare to not share my notes with them, I suddenly become the meanest person in the world.
In Early Modern English grammar, you could use inversion instead of an if clause to create a counterfactual.
I could not love thee, dear, so much, loved I not honor more.
In contemporary English, this would be
I could not love you, dear, so much, if I didn't love honor more.
We still use inversion instead of if clauses for past tense modals and auxiliary verbs:
I could have borne the shade, had I not seen the sun.
We don't use inversion instead of if with present tense modals or non-counterfactual conditionals. So we don't say
*I will help you, can I find the time,
I would help you, could I find the time,
is grammatical (if a little old-fashioned sounding).
I don't believe people ever did this; I haven't found any use of inversion for non-counterfactual conditional clauses (although maybe I didn't look hard enough).
Here, dare is indeed a semi-modal. But it's not a past tense modal and this isn't a counterfactual conditional clause.
So I don't think this would have been grammatical in Early Modern English.