Why do some people have iOS 7 already?

I have an iPhone 4 and so does my friend and he has iOS 7 already. Also, I know a lot of other people have it. What is the reason and when can I get it

This - http://m.iclarified.com/entry/index.php?enid=30995

2 ways… Become a developer or get developer status… Or… Pay $99.99

your choice

He has the Beta version. You can make a developer's account and buy iOS 7. Its not for $99. However, I wouldn't suggest you to get it. The Beta version is basically the second stage. This is the stage when the OS will be debugged to make it buttery smooth. Right now there might be certain problems. You should wait for its official release. Hope this helps.