Just to comment briefly -
AB contacted me via private email a little while after they and Somey and Charles received the emails. I and WMF persons are taking this seriously. Somey forwarded emails (same ones posted) and I talked to Charles briefly.
AB does not wish to file a police report, which would necessarily require identifying themselves. I respect their wishes, though I would like to pursue this to identify and have the threatening party prosecuted. This sort of behavior is unacceptable.
If anyone else associated with the project receives threats of this nature, or believe that you know who sent these, please contact me, senior administrators, Arbcom, or the Foundation.
I emailed AB after this thread started and before commenting here and they were comfortable with a brief public comment about this, but would like me and others to respect their privacy.