A user reaches Thales as a market creator if the user initiates a brand new market by depositing sUSD and mints an equivalent number of sLONG and sSHORT options position tokens, the will earn a percentage of the total pool size (open interest).
A market creator cannot just mint one side of a market. A maker creator can only mint sLONG and sSHORT tokens at the same time.
In the current implementation of the Thales protocol when a market makers increases the pool size of an existing pool there is a 0.5% fee of the sUSD amount that goes to the market creator and there is a 0.5% protocol fee for ThalesDAO.
The only difference between the market maker and market creator from a technical side is the market creator started the pool first. Both creators and makers always mint both types of tokens.