EasyRetroPGF is built on Gitcoin's Allo protocol.
This protocol also powers the full-blown Grants Stack platform for creating/managing, applying, and donating to grant rounds and public funding initiatives.
EasyRetroPGF uses Allo to process and handle token distribution. More information on Allo can be found in the docs, with code and contract addresses available in the open source repo.
EasyRetroPGF is open source and can be readily contributed to. Users are encouraged to open Github issues, reach out in the Gitcoin Discord, or fork the repo to implement their own modifications.