The front page is not allowed by the work proxy... the forum gets through. 
I see why.
The main site page has a lot of keywords in the meta part of the code such as game, console, downloads and hack. All of which are considered naughty words in the eyes of company IT departments and on the block list.
The forum page alone however has just this:
PHP, MySQL, bulletin, board, free, open, source, smf, simple, machines, forum
Nothing fun about those words so the page is not blocked.