Are there any for-pay (commercial) but open source applications in Ubuntu Software Center?

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http://askubuntu.com – I've recently decided to try not to support any proprietary software, and see how far I can go with Free software. Despite this, I realize Free software costs money to make, and would be happy to pay for some. Is there any way to sort through the software in Ubuntu Software Center to find some, or if not, what applications are there are there? (Examples would be great) Thanks! (HowTos)