@Mor - Actually, they offer it to anyone who asks to be certified. So, they don't get money from sales of the software that is certified. However, the certification has to be renewed each year, so they probably charge a fee for that.
It used to just be formatting the addresses to ensure they were accurate, which is quite a simple task. Now it's slightly less simple because it will actually check to see if the address is a valid one, and even check against the post records as to whether it has been changed recently.
Considering how huge the United States is, and how many addresses there are to check against, that's pretty good, I think.
And I suppose if the software has to link to other computers it would need to be checked every year.