So being you're an X 350Z owner, you'll understand as well when you see a Z that's badged as 'Fairlady' too..
http://en.wikipedia.org/wiki/Fairlady_Z

 

Doesn't JDM stand for Japanese domestic market? Not OEM

 

It does, but back in the days, JDM Integra usually ment what I posted earlier. as USDM being coverted to a JDM integra by importing the full front end of a JDM integra..

People were installing Japanese aftermakert parts since way back when but they never called it JDM.. They called it "aftermarket parts"..

JDM back in the days, again, referred to isntalling JDM oem parts... Hence the term JDM integra. etc etc..

What people are doing now to the G35, I wouldn't call in JDM, I just call it aftermarket.. Just like everyone else.. But, there are a couple of ricers on EBAY labeling everything JDM just to get people to buy it.. haha

 

OP understands and this topic has been beaten to death.