This is what is says exacly on the website. A fork of remastersys or better Remastersys itself. for now the remastersys package for x64 systems has a little deppendecies issue. So you can't install it trough the software center. You have t o do ist by hand with dpkg - i <packagename> and then ran apt-get install -f to fix the issue. For this time ther is not moe to say here because there is no difference between remastersys and os4systemimage yet.