How do free and open source projects earn revenue?

Most good programmers do programming not because they expect to get paid or get adulation by the public, but because it is fun to program. -- Linus Torvalds

Ever wondered how commercial companies which develop open source software make money? How are they able to thrive in today's competitive world (with competitors employing tactics such as Fear, uncertainity and doubt, Embrace, extend and extinguish etc). Here are some ways using which free and open source projects get their revenue:

1. Donations (from users).

2. Microdonation providers such as flattr and Gittip.
3. Crowdfunding such as Bountysource.

4. Advertisements on project's website.

5. Another possibility (typically used by operating system (distribution) vendors):

• Ubuntu changes default search provider for firefox 
• Linux Mint using Google Custom Search Engine 
• Linux Mint default search engine in Linux Mint 12 to DuckDuckGo

6. Paid support: Provide support to customers in return for money.

7. Octave dev demands money to release bugfix that he already wrote (post on /r/programming)