Nuke is essentially a successor to Shake, which was basically a cheaper alternative to whatever Sony, Avid, and Qauntel were pushing way back when. Natron is a

Nuke is essentially a successor to Shake, which was basically a cheaper alternative to whatever Sony, Avid, and Qauntel were pushing way back when. Natron is a node-based compositor, there have been many over the last few decades. Another open source node-based compositor is Blender which also has an non-linear editor. Lots of compositor customers just buy Nuke, Fusion, AE, etc to process sequences through different commercial plugins; having an open source wrapper to run and control the plugins is an excellent alternative.