The Gateway Software Stack (GSS) is a middleware implementation of the ATSC 3.0 Interactive Content specification using the Vewd browser and Vewd DASH media player. The GSS is a ST418 Linux port for the PILOT Gateway proof of concept ATSC 3.0 receiver. The GSS is meant for systems integrators and vendors who wish to build an ATSC 3.0 receiver. The GSS middleware could be ported to other browsers or hardware platforms.