1)For what I understand from the TN, the license is only necesary to be able to send reputacion information to Symantec, but not for the normal function of the product. Am I correct? - Yes
2)Also, if I install the license in the unmanaged clients, do they count as a seat for the license?
as its unamanged it wount report or take license from SEPM, you need to install the license locally on the box.
apart from exporting the unmanged package from SEPM, SEPM and client don't talk to each other