Google ARCore - Google Augmented Reality SDK
openDesktop.org - The website openDesktop.
Vuforia SDK - Vuforia is a vision-based augmented reality software platform.
SourceForge - The Complete Open-Source and Business Software Platform.
Wikitude SDK - Wikitude’s all-in-one AR SDK combines 3D tracking technology (SLAM), image recognition and tracking, as well as geo-location for apps.
Eclipse - Eclipse is an open source community, whose projects are focused on building an open development platform comprised of extensible frameworks, tools and runtimes for building, deploying and managing software across the lifecycle.