Serum DEX's operations remain unchanged. Serum Swap was an adjacent function that was built for others to use. It was never a core component of Serum. Swap alternatives built on Serum include Orca and Raydium.
Serum Swap is a new AMM on Serum. Like typical AMMs, you can join the pools as a liquidity provider or trade against them. The curve is the standard x*y=k curve. Serum Swap is fully on-chain and non-custodial.
Solana-based AMMs are fast. Serum Swap takes about 1 second to settle a trade or pool addition/removal, and gas fees are tiny—roughly $0.00002 per trade.
You can find the source code on Github.
Takers are charged 0.30%. Of that:
0.25% goes to the liquidity providers (LPs).
0.04% goes to a SRM buy/burn.
0.01% goes to the GUI hoster; you can set this in the GUI source code.
Serum Swap is not the only Serum AMM. Other projects include:
While Serum Swap has been tested, it has not been audited. Use at your own risk.
Furthermore, the GUI you use might not always give clear reasons for error messages. When in doubt, check your max slippage.