HST is an open-source project. This page contains several links that will be helpful if you'd like to contribute.
The HST code is hosted on Github. The easiest way to contribute code is to fork the project on Github. You can also clone the HST repository using the following command:
git clone git://github.com/hst/hst.git
You can use Github's “Pull Request” feature to send in patches.
If you need to report a bug, please use HST's Lighthouse project.