Trying to make it a bit more clearer:
Every one can add modules to My modules, but you need a Unicorn account to add modules from the My module page to your rack.
Clicking on a module in the All modules tab redirects to the module detail page while clicking on a module in the My modules tab adds that module to your rack. If you don't have the Unicorn account you will be redirected to the order page.

... and thanks for supporting!

Beep, Bopp, Bleep: info@modulargrid.net