A 3ds Max DR Render slave is the application that allows you to render using Distributed Rendering (DR) – which is the process of rendering a single frame on multiple computers.
V-Ray Standalone allows you to render without having any 3d platform installed (Max, Maya, Rhino, SketchUp, etc.). Standalone supports all V-Ray options such as Distributed Rendering, RT, and others. V-Ray Standalone is a console application, meaning it does not include an interface and it can only process/read files in .vrscene format (a special V-Ray format which is the 3d scene exported to .vrscene by the V-Ray plugin). Thus if you want to use Standalone, it is necessary to own at least one license of V-Ray for Max/Maya.