Any business that takes even 1 cent from someone and gives it to someone else is, by the definition provided on the url I shared above, a MSB. GoFundMe certainly is. Yelp is not, but they are culpable by this business business arrangement.
From my link "a person who engages as a business in the transfer of funds is an MSB as a money transmitter, regardless of the amount of money transmission activity." (emphasis mine)
So, YES. Did you just stop reading after your bias was confirmed?