There are no restrictions in place on the .org top level domain. It is open to any person or organization. Which really means that anyone, anywhere in the world can register one. While a lot of nonprofits will uses a .org domain, seeing it does not mean that site is for a nonprofit.
This TLD is managed by the Public Interest Registry, along with the newer .ngo & .ong options. These domains require validation of the registering organization prior to the name being licensed. You can read more about that here.
