Treeline is now fully open source. You can find the complete codebase at github.com/treeline-money/treeline.

Previously, Treeline was “open core” - the core logic was open, but the desktop app code was closed. I originally chose this because I wasn’t sure how I wanted to support the project long-term, and figured it’s easier to start closed and open later than vice versa.

I’ve since landed on a simple principle: if it doesn’t cost me to run it, there’s no reason to charge for it.

The core app will always be free. I may add optional paid services in the future, but only for things that actually cost me to host—like cloud backup or multi-device sync.

Why open source matters for a finance app

Transparency. You’re trusting this app with your financial data. Opening the codebase means you can verify I’m not secretly harvesting data or doing anything sketchy.

Contributions. Finance is personal, and everyone’s situation is different. I’m US-based, so I can only feasibly test scenarios I encounter personally. Open source means folks can submit fixes for edge cases I’d never see—different banks, currencies, date formats, and more.

Security. More eyes on the code means vulnerabilities get spotted faster. Anyone can audit it.

Longevity. If I get hit by a bus or lose interest, the community can fork it and keep it alive. Your financial workflow shouldn’t depend on one person maintaining closed software.

This feels like the right move for a project like this. I’m excited to see what the community builds and fixes that I never would have thought of. Check out the repo at github.com/treeline-money/treeline.