Yapeswap v1 is a fork of Uniswap v2 that fractionally deposits the reserved tokens to Yearn finance. All source codes are released under GPL & MIT license. Please visit https://github.com/yapeswap to check contract codes. And here are important code diffs between Uniswap & Yapeswap that you have to check.
Smart contract audits are soon to be in progress and will being funded by the Yapeswap DAO treasury. The core contributor team is in the process of selecting a third party audit firm. Audits are expected to be complete by the end of September, 2021.