The Headlamp can be turned off one of several ways.

1. Add a light to the scene. This will automatically turn off the headlamp. a. Note this has to be an actual light, not an HDRI Map, not a mesh light created by adding emission to a surface. b. This light can have an emission value of zero or be made invisible (which means it is off and emits no light.)

2. Under render settings, under "General" there is a line that says Autoheadlamp Set it to never.

I personally created a scene called Default which has an invisible pointlight in the scene. I then opened it in a text editor (after using 7zip to uncompress it) and removed the authorship information. This way I will not accidentally overwrite it. Then I gzipped it and put it back. I set the preferences to open this scene whenever DAZ Studio starts and whenever I hit new. Now I never see the headlamp. :)