I checked it out. It says, "Enhanced by Google." I assume that means Startpage interfaces with Google for a more comprehensive search?
Startpage sneaks into Google, gets your answers for you, and returns them to you with no strings attached from Google. It’s a private search engine, and Google never knows it was you.
Go to the Startpage home page and click on “Details” just under “Enhanced by Google”. It will explain how Startpage works for complete privacy.