***PLEASE IGNORE THIS INCORRECT RESPONSE.***
If you're saying you want to redeem the license activation code that the other person bought, under their own email, into your iLok account, no I don't think that works. [WRONG. SEE MARTIN'S REPLY.] The license is registered to the purchaser's email address, and I'm fairly sure they'll have to create an iLok account with that same email address to redeem it. After that, they could pay a fee (to iLok and to MDA) to transfer it to your iLok account if you're actually going to be the owner and user. Bear in mind that a Hauptwerk license in iLok is for one user (and one computer at a time), not to be shared by different people.
If you're planning for the other person to be the user, read on...
I don't think the email you used on the download form for the trial copy, or the one you gave iLok to activate the trial license, will have any effect on who can use their own full license. The email isn't embedded in the installation file, for example, since everybody downloads a copy of the same file (either for PC or Mac).
There are two independent licenses here, your temporary trial license and the other person's full license. Nothing ties them together.
You should be able to install Hauptwerk from a copy of that same installation file on another computer (if it's the same OS type, i.e. PC or Mac), and your other party should be able to run it with their own license activated under their own iLok account. They should also be able to run your computer's HW with their license if they switch the license over by inserting their iLok USB key or logging into their iLok cloud account on your machine. It's really pretty flexible.
You can actually install HW on as many of your computers as you want, because one license only allows one copy to run at a time, enforced by iLok. The Hauptwerk 8 Installation and User Guide covers licensing near the beginning of the book.
Hopefully somebody will correct my if I got any of that wrong.