http://gradschool.brown.edu/go/tuition
"Tuition Requirements for the Master's Degree -- Master's degree students must pay tuition for a minimum of one year of full-time study. Some programs require more than the minimum of one year of full-time study."
That was the case for years, so I suggest you to double check with the The Office of Financial Aid.
I want to correct one thing:
As far as I remember, at Brown, if you are an international student, you can't be a part time student in your first year. Are you sure that is the case?
Well, I got the same batch e-mail, and I already know that I am rejected (from an insider). So if you have not been contacted before, it is most likely a reject email..
I just checked my spam folder and I don't have anything. I am an international student but I live in LA so that is not a good sign.
By the way, when exactly did you get the invitation email?