I'm in the process of listing Megalytic in the Google Analytics App Gallery. They require a page that explains in "plain language" how we access a Google Analytics account and what we do with the data. So here it is.
How Megalytic Accesses a Google Analytic Account
Metalytic uses the Google Analytics API and authorizes via OAuth 2.0. That means we don't store your user name or password for Google Analytics.
Megalytic stores you Google Analytics data in a secure database in the cloud. Essentially, we cache this data for you, so that you can access it whenever you want. When you use Megalytic to download your Google Analytics data, it gets downloaded from the Megalytic database - rather than directly from Google Analytics. Megalytic runs a nightly batch job that keeps its database current with your Google Analytics account.
If you decide to stop using Megalytic, you can revoke the product's access to your Google Analytics account by clicking on "Edit" next to the "Authorizing applications & sites" section in your Google account settings page (https://www.google.com/settings/). ; The "Edit" link is shown below.