SAN FRANCISCO, Aug. 10 -- For the first time in the United States, Android users can download a third-party app store directly from Google Play. The feature went live on Sunday, placing a store called Aptoide Games one tap away inside the same marketplace where people find their standard applications, without any developer settings to enable or extra prompts to navigate.

The practical change is narrow. Aptoide Games, which carries free and paid game titles, appears in Play Store search when you type "App Store," on a dedicated landing page, in the account menu, and inside the apps category. Tapping it begins the same install process as any regular Android application. When the installation finishes, a second app store lives on your phone...