it's a mess... because it's over 3 years since the last release of MDT it's not "officially" dead and no longer supported... fantastic news for all of us long-time Autodesk customers with MDT datasets and personally think it's a massive joke. They're happy to spend time adding import tools for other software to try and poach new customers but any long-term customers with old data are left screwed with no import tools built within Inventor
I've not had to reinstall the systems here (and still on Iv2012) so not had the pleasure of trying to register MDT again recently or trying to get it to work with Iv2013.
From posts here, afaik, you need Iv2012 installed to install and register MDT2009, so (from memory) the install process is something crazy like:
install MDT2009 & register it
but, there's some problems along the way:
1) Apparently... Because MDT is no longer supported you can only activate it if you have an active subscription which goes back to when MDT was supported (ie Iv2012 or earlier) - so, if you buy a new licence today i don't think you can register MDT, even if you had a licence for it "back in the day"
2) Because MDT is no longer supported there's no official import of MDT files into Iv and thus the dwg option has apparently gone from the file-open dialog... But, by drag and dropping the file into Inventor it still brings up the dwg import dialog box (until they remove that...)
^ that's my knowledge from these forums since the release of Iv2013 (which I've not yet dared to install because of this mess) and all posts/comments from other users (and guess it's a VAR mentioning the requirements of an active subscription going back to MDT). As far as I know there's been no official help/advice from AD about this and no mention of what we are to expect in the future when we need to register MDT anytime we wipe/upgrade our systems. Thus my topic:
As a thought, he could also pay you to convert the MDT to Inventor one time. This will depend on the client's usage of that MDT dataset obviously. We have been doing this pretty regularly for our clients as a service.