Yesterday I downloaded Mango core 2.0.3 from http://infiniteautomation.com/index.php/download.html and from http://m2m2.serotoninsoftware.com/core, after trying to unzip it with winrar, I was asked for password.
I downloaded it again this morning, and no password was requested. I'm not sure why this happened.
Anyway, problem solved. Thanks :)