With many video editors on the market, GPL Open Source alternatives are limited. However, Blender does a great job here. Blender? Yes, Blender, that 3D modeller. Now you probably lost me, I understand. But take this from me, their build in video editor is one of the best available And you don't even notice that you are inside a 3D modeller. There is a one major drawback: The interface is a bit stubborn.