Surf never takes a commission but the Everscale blockchain does.
In the Everscale (formerly Free TON) blockchain, the commission is charged for:
Surf automatically calculates the commission for your transfer. The transfer fee is paid by the sender. It depends on the amount of the transfer and is quite small.
When you transfer tokens, use DeBot or send Evers to staking, you launch certain smart contracts. The execution of any smart contract on the Everscale blockchain is paid. This fee is called “gas” and is paid in Evers. The more computing power is used by the smart contract you have launched, the higher the commission for its execution is.
Your messages in the Surf chat are not subject to commission.
You can read how fees are calculated on the Everscale at zeroheight.com.