As a dev at a large company, I'm wondering how the author went about open sourcing the side project. My employment contract stipulates that anything I write for work is owned by the company. This company wouldn't have any motivation to let me open source the work I do, which in my case does not go into any product.

The reason I ask is that I have written, as part of my day job, a scientific library in C# that doesn't appear to have any public equivalent and I know addresses common tasks in the industry. I would love to open source it, if not for beer money, but for visibility to help my career --- I'm at that point where promotions only happen with externally-visible accomplishments.