(This is Dan from CFAR)
Yep, you're definitely free to run a reading group on the handbook.
You can basically just treat it like any other book. CFAR made the handbook as a supplement to our workshops, and we put it out there so that other people can see what's in it and make their own calls about what else to do with it.
Pretty confident CFAR would be okay with this. But of course someone from CFAR could say something more confidently.
The CFAR handbook is a great resource for applied rationality. I talked with another rationlist in Berlin about creating a reading group around it. Did CFAR articulate a position around how the handbook can be used and whether such a group would be okay? If so, are there any norm such a reading group should fulfill (e.g. making it clear it's independent of CFAR)?