Dual licencing
For those concerned how MySQL could be worth $1bn when it "gives its products away for free"..
You are overlooking the fact that MySQL is available under a dual licence. Those who incorporate MySQL into a product distributed under a non-free licence must pay for the Enterprise edition of MySQL. Similarly those who want support and a more traditional relationship with their database supplier (MySQL) can pay for the Enterprise Edition.
If you do not distribute your product or distribute it under the GPL then you can use the free (in both senses of the word) version of MySQL.