Please bare with me So after purchasing my copy of DG online (the digital download copy, obviously) I realised I couldnt actually download it as my houses net useage for the month is too close to it's limit.  To remedy this, I installed impulse at work (with the bosses permision!) and downloaded the game straight to archive on that computer, and brought it home.

Now...My friend bought it at the same time, and we assumed that we could use the same file to install on both of our computer but when he logged into his impulse account it said it wouldnt extract the archive.  My assumption is that my personal serial is already in the file that was downloaded using my impulse account?  Anyway... I logged onto his computer with my own account and unpacked the game, and then let him switch back to his own account. BUT... Was this okay?  Will the SD servers be registering me as having installed my game on like three computers now, eventhough it's only being used on my own computer, and on my friends with his own serial purchased?

After he logs in his own account it shows his serial when you look at the registration info, but since it was installed with me logged in first, and downloaded through my account is my serial somewhere still in that install?

There seems to be a lot of info in random places around google about how the "share it with your LAN, that's cool" policy, but there seem to be strings attached, and I'm not sure if I'm crossing the line now and my mate will have to uninstall to redownload again through his own account before his Impulse considers it as using his own serial. 

Any chance of getting an authoritative response? I'm trying to do the right thing.