Zeebe is available as Open Source Software on GitHub.
Zeebe welcomes extensions and contributions from the community!
...along with other integrations such as Spring-Zeebe and the Apache Kafka connector.
If you built something for the Zeebe ecosystem, we encourage you to add it to the Camunda Community Hub using the 'New Community Extension Proposal' template.
If you're interested in contributing to the main Zeebe repository (vs. creating an extension that lives in its own repository), be sure to start with the "Contributing to Zeebe" guide in GitHub