VDMX is described as '5 was created from the ground up to meet the demands of realtime video performance. Built around a robust data processing architecture it was designed to be used with whatever hardware- or software- you've got available'. There are more than 10 alternatives to VDMX for Windows, Mac and Linux. The best alternative is Pure Data, which is both free and Open Source. Other great apps like VDMX are Max/MSP (Paid), Vvvv (Free), TouchDesigner (Free Personal) and Isadora (Paid).
Pd (aka Pure Data) is a real-time graphical programming environment for audio, video, and graphical processing. It is the third major branch of the family of patcher programming languages known as Max (Max/FTS, ISPW Max, Max/MSP, jMax, etc.
vvvv is a graphical programming environment for easy prototyping and development. It is designed to facilitate the handling of large media environments with physical interfaces, real-time motion graphics, audio and video that can interact with many users simultaneously.
TouchDesigner is a complete authoring tool for building interactive 3D art, visualizations, prototypes and UIs. Derivative makes and supports TouchDesigner and offers their services to do custom production using TouchDesigner.
Orca is an Esoteric Programming Language and live-coding environment for musical experimentation. In Orca, each letter of the alphabet is an operation, lowercase letters operate on bang, uppercase letters operate each frame.