How to record soundflower from OS X?
Tracking down the correct forks of this semi-dead project was indeed tricky.

I installed the Kernel Extension from here:
https://github.com/mattingalls/Soundflower/releases

I installed SoundFlowerBed from this fork:
https://github.com/mLupine/SoundflowerBed/releases

That puts an item in the menu that allows you to set SoundFlower (2ch) --> Built-In Output, which then makes "SoundFlower" available in QuickTime Player etc.