At Balsamiq we are big fans of open source software. We use a lot of it to power our business and our infrastructure, and we try to give back to the open source community whenever we can:
We open source parts of our code and tools, usually with MIT licensing. Visit https://github.com/balsamiq to find out more.
We also open-sourced the font we created for Balsamiq Wireframes. It's called Balsamiq Sans, check it out!