[fwenzel]

Hard to answer that as I lack your exact frame of reference.

Generally, employees of Mozilla Corp. are paid (and managed) to contribute to specific aspects of the Mozilla project. Sounds confusing, but essentially, imagine there is a new feature for Firefox browser's rendering code that needs implemented -- it's open source so technically anyone can submit a patch, but Mozilla-the-legal-entity may opt to hire and pay you to fix it (and many more after that).

You are then a professional software engineer working for someone who would like to reach a certain goal (such as: A new release of Firefox!) and gives you money to help them achieve it.

Edit: For disclosure, I should have mentioned that I work at Mozilla.