There seems to be a problem for Soundflower on El Capitan - if you open up SoundflowerBed (a separate program), it will declare "Soundflower not installed". Whilst I tried a couple of fresh installs from Github repos and MattGalls
1. uninstall Soundflower
3. Open iShowU HD, clicking on applications to record prompted a request to install Soundflower.
so the driver for OS X 10.11 seems to be included in this application. And works fine