The search engine isn't currently open sourced as we're still a small project and don't want to get wrecked by competitors at such an early stage, but you can contribute by creating packages that layer on top of the search engine - you can see a few of those here - https://presearch.io/packages. You can search any cryptocurrency through presearch.org and see a community package that one of our community members made. Here's the github link to the community package code as well!
https://github.com/PresearchOfficial/presearch-packages