It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

Is there any way to access the beta branch? Or is it steam exclusive?
there is an option to enable beta channels:

more -> game settings -> and here on the line of "configure game" on the right hand side.

however, as of yet no beta-update (4th character) is available - ah well, patience is a virtue, is it not :p
Could anyone tell me if the 4th character update is available yet on the GOG beta branch?