Some people say ANYONE can take the LEED Green Associate Exam, is it true?

The short answer is: Yes.

If you are taking LEED Green Associate Exam, you need to meet one of the three criteria below:
1) Studying in an education program that addresses green building principles

Per USGBC:
“GBCI has confirmed that all of USGBC’s education programs, with the exception of its webinars, satisfy this requirement.” See link below for more information:
http://www.usgbc.org/DisplayPage.aspx?CMSPageID=2011

This means ANYONE can take the LEED Green Associate Exam.

Why?
Because ANYONE can take the one of the USGBC’s education programs listed at link above and qualified for the exam as long as he is willing to pay the fee (about a few hundred dollars, exact fee is depending on which program he chooses). You probably will take one of these education programs to prepare for the LEED exam anyway.

OR
2) Working in a sustainable field

OR
3) Have previous experience supporting a LEED-registered project

Quoted from page 25 of “LEED GA Exam Guide”