Would anything really happen if he did go through with the DMCA? [...]
Technically ripster committed copyfraud by issuing a false DMCA notice since CC-BY is non-revokable meaning GH had a valid license. Copyfraud is a criminal offense so if iMav wanted the headache he could have pursued the matter.
The reality is there was nothing to gain by doing so, and rootworm had destroyed the wiki anyway.
Just remember kids: licenses have terms, and summoning the DMCA Demons should not be done lightly.