0x Tracker is fully open source and can be found on GitHub, making it easy to contribute changes. The platform is comprised of a few different projects: 0x Event Extractor, 0x Tracker Worker, 0x Tracker API, and 0x Tracker Client.
Heading over to the GitHub organisation will allow you to dig into the codebase of each project. Javascript is used across the entire stack, making it easy for anyone familiar with the NodeJS ecosystem to contribute across the entire suite of projects.
If you are keen to contribute but do not know where to start then be sure to check out the existing issues in each repository. You can also get a better understanding of current initiatives by looking at the organisation's projects.