Google has recently announced that end users will now be able to access and install apps from the Google Marketplace for their accounts. If an app requires Admin access in order to run ( such as gPanel ) end users will not be able to install the apps. 

However, you have the options to either disable this new access entirely or to only allow end users to install previously white listed apps from the Marketplace. 

Google's instructions for accessing these settings as well as white listing apps can be found here