If you’re annoyed by the nag dialog that pops up when you log into your Proxmox 3.1 community install, run this patch from VM server in question.
wget http://www.tolaris.com/blog/wp-content/uploads/2013/08/no_subscription_popup_pvemanagerlib.js-3.1.patch -O - | patch -p0
Piping that download through patch, will apply the fix to the appropriate file (/usr/share/pve-manager/ext4/pvemanagerlib.js)
Log out of the web UI, and possibly clear your browser cache / close browser window.
Having said that, there is support from Proxmox available if you feel guilty about using the patch.