You should take some time to read the owner's manual. According to what I see, the rear brake on the bike is a wet brake which typically requires special oil and not a "standard" gear oil. I used Shell Spirax S4 TXM in my 2010 Kawasaki Brute Force 750 with great results. I would assume something similar would work in yours provided it meets the specification.
However, if you have a warranty, I would simply buy the Yamaha oil and not risk it (at least until the warranty expires).
Regardless, there still might be some good info you can get from the site? (Yamaha section or Tech tips)
And also, even though this one looks quiet, I am sure there are others around if you Google them or just Google what you're looking for, and I am sure something will come up.
I had an 05 Grizzly and my Father an 05 Kodiak and used Amsoil Severe Gear in mine but maybe things have changed considerably since then as far as fluids go?