If you're specifically interested in hacking on open source software in the financial/algo trading space, Quantopian also maintains Zipline, which is an open so

If you're specifically interested in hacking on open source software in the financial/algo trading space, Quantopian also maintains Zipline, which is an open source backtesting/financial simulation library. We'd love to get pull requests and/or feedback. You can find the source on Github here: https://github.com/quantopian/zipline https://github.com/quantopian/zipline Disclaimer: I work for Quantopian and I'm a Zipline maintainer.