As CNET points out, Facebook Friend Exporter technically violates Facebook’s Terms of Service. Section 3.2 states the following:
You will not collect users’ content or information, or otherwise access Facebook, using automated means (such as harvesting bots, robots, spiders, or scrapers) without our permission.
Mansour doesn’t care about this, as he says in the extension’s description:
Get *your* data contact out of Facebook, whether they want you to or not. You gave them your friends and allowed them to store that data, and you have right to take it back out! Facebook doesn’t own my friends.