$ whois themeforest.net
Registrant Organization: Envato Pty Ltd
Registrant Street: PO Box 21177, Little Lonsdale St
Registrant City: Melbourne
Registrant State/Province: Victoria
Registrant Postal Code: VIC 8011
Registrant Country: AU
Registrant Phone: +61.390230074
Registrant Phone Ext:
Registrant Fax: +61.290183043
Registrant Fax Ext:
Registrant Email: domains@envato.com
Envato has a page on DMCA takedown notices, but I'm not done reading it
yet. None the less, it seems they may respond to DMCA Takedown Notices.http://support.envato.com/index.php?/Knowledgebase/Article/V...
The important thing is that filing a knowingly false DMCA Takedown Notice can have legal consequences, both civil (read: monetary) and criminal (read: prison).
http://www.aaronkellylaw.com/internet-law/consequences-of-fi...
Personally, I'd contact ThemeForest/Envato myself to let them know I'm being harassed with threats of false complaints before the other guy gets a chance to file his false complaint.