Polkadot launched dotUSD on mainnet after DOT holders approved it through OpenGov Referendum 1944. The stablecoin has no private issuer, but its first phase depends on USDT: users can mint dotUSD one-for-one against USDT and redeem it for $1 worth of USDT, subject to an initial supply cap.
The approved rollout includes a DOT-dotUSD liquidity pool and treasury funding to support liquidity. A later, planned phase would let users mint dotUSD against locked DOT and add price oracles and liquidations; those features are not part of the initial phase.
