We do this at 99designs. Anything that isn't a core piece of domain specific tech related to running a design contest—we'll open source it. We don't just do it

We do this at 99designs. Anything that isn't a core piece of domain specific tech related to running a design contest—we'll open source it. We don't just do it for goodwill either — it's a great design practice. It's good to design systems that are built out of components that are small, single-purpose, well tested etc. Making a component open source helps you define it's responsibilities and separate your concerns better.