That was not their duty to do that. they were not on a pay roll, and nobody assigned that project to them. It seems they wanted to do some kind of commitment. Nice to see some people works not just for money, but for a higher good. I wish more people, and not just in software industry, have this kind of motivation.

You'd be amazed to see how much time some people spend on free software projects.

Exactly.

I'm amazed by the effort that they went to, sneaking into the building to work on the code. I'm also tickled by the fact that other employees helped them, and knew about their situation despite the fact that the big shots in charge didn't.