Easy, have them register and they will have their own key sent to them.

Your key is unique to you and your email address. The fact that you had the keys sent to the same email (your), it is recognised and the same key (yours) is sent again.

Don’t forget they have 60 days use without a reg key. The total file size of the download is only about 8MB so should only have taken about 32 - 40 minutes, even on dial-up (that is what I used).