1. Join a company (usually big) that has a culture of open sourcing softwares.
2. Start an open source project you are keen on, and make use of the resource to grow the project/community/contributors.
3. Quit with other core maintainers and start your own company that commercializes the open source project.
Remember also, that large companies have experimental expansion phases which they usually abandon once economic crisis dawns. If the thing you build is such a "experimental fort" - your parent company might be open to a "buy out", were you promise them favorable conditions by your future company with whom they share the IP.
