From that article:
The switch to Open Source software was primarily driven by costs, and MySQL was found to be the most robust product available
Well, since MySQL is free and Oracle costs a bundle, and you are limited by cost, which one would you choose?

I suppose when they compared free databases, they found that MySQL was definitely more powerful than manually editing a text file with notepad .

All modern RDBMSs' are multithreaded, client/server systems, and whoever wrote that MySQL help file that says MySQL is as powerful as Oracle is on crack! Also note the source of that document (mysql.com)

For a free database, I'm definitely not going to complain, but there is alot of hype about mysql. I am not claiming to be a MySQL expert, but from what I understand about its limitations I can't see how this can be considered a contender to the big boys (Oracle, M$, IBM, Sybase) when you need anything more than table storage and some simple queries.