Depends on the market. The following ones have definitely seen open source win: Servers (as mentioned, various Linux distributions with things like Apache also

Depends on the market. The following ones have definitely seen open source win: Servers (as mentioned, various Linux distributions with things like Apache also being open source on top of that) CMS systems (WordPress, Drupal, Magento, MediaWiki et al) Programming Languages (virtually no one pays for one anymore) Source control (Git) Web browsers These are dubious though: Mobile (Android is open source, but iOS still holds a decent percentage of the market) Enterprise software And I don't think the gaming world has been won by open source software just yet. I don't see Nintendo/Sony/Microsoft/Valve open sourcing their dev kits/OS software/firmware/whatever, and those companies dominate most of the market.