It's not as if he's even complaining that the DHS is using *his* software - it's that they're using Chef, for which his software is an optional (but convenient) cog, so he does something to spite all Chef users.
How far do you go with this? DHS are using Ruby. Should everyone pull all Ruby code that's ever been published? Are DHS using Red Hat, or Ubuntu? Should we boycott those companies too?
HST, Chef were wrong to remove the primary attribution when they copied it.