WordPress started in 2003 with a single bit of code to enhance the typography of everyday writing and with fewer users than you can count on your fingers and toes. Since then it has grown to be the largest self-hosted blogging tool in the world, used on millions of sites and seen by tens of millions of people every day.
WordPress is open source. This is not the same as free, the great thing about it is that it is free to use in the sense that you can do with it whatever you want. This freedom allows you to take the code, modify it (or not), repackage it, distribute it. It’s up to you.
I have over 8 years experience working with WordPress developing and maintaining various blogs and websites for businesses and charities. Have a look at my clients.
I am also proficient in modifying plugins, themes and widgets for wordpress and have recently started making my own. My first (of hopefully many projects) being the Simple Download Monitor Widget.