"While we decided a long time ago that we wouldn’t be open-sourcing the core Stack Exchange Q&A engine, we do try very hard to open source as many useful parts of our code as we can.
As Stack Overflow is one of the most prominent Microsoft .NET-created sites for software developers in the world, we feel that it’s part of our mission to help lead fellow .NET developers — and the most effective way to do that is by contributing some of the code that we use to build Stack Overflow and Stack Exchange back to the greater .NET developer community as reusable open source packages. This isn’t just a fundamental part of every Stack Exchange developer’s “be more awesome” plan, it’s an explicit goal embedded in the very DNA of the company.
In fact, over the last few years, we’ve contributed a number of useful open source projects back to the world:
- MarkdownSharp and PageDown
- Data Explorer
This is a great list of OS projects and example for other companies. Keep your primary revenue generating source close to the chest, but for other projects, libraries, utilities think about letting them out of the firewall (I.e. release their source). We're all standing on the shoulders of giants, if you're willing or able to admit/acknowledge it or not. Releasing non-revenue IP lets you pay it back and forward...