I mean, also Blender (written in pure C, Python scripting for UI). Pretty sure it's as complex as Wolfram at that point. Largely financed by private corporation

I mean, also Blender (written in pure C, Python scripting for UI). Pretty sure it's as complex as Wolfram at that point. Largely financed by private corporations now, still open source. The irony is that Blender USED to be a proprietary project, the community had to buy back the source code.