Haul is an upcoming Arcade game that will be obtainable on Grok's page in the near future. The release date hasn't yet been revealed, but with MLN's gradual lack of updates, its release seems unlikely.
The MLN Arcade page gives the following information about the game:
Haul Arcade Game
This My LEGO Network Arcade game requires some heavy lifting! Create a mind-bending platform puzzler for your friends to play through. Place gates, triggers, bricks and ladders to make your game unique. Coming Soon.
How to Obtain
No one knows when the Module will be released. All that is currently known about Haul is that it will be obtainable on Grok's page.