1 - problem with signup ( 'Don't leave any fields blank') is fixed - admin of HT said that on their forum
2 - yes, it is a polish site, and NO it is not closed for non-polish users! There is no such thing like ban for all non-polish proxy etc.
But if proxy is banned.. (403 error) - it's just like on BitmeTV - someone cheated, lost his acccount, and proxy he used (often whole proxy range) is being banned.