Logic 9 hooks itself fairly deep into your system, so the 40GB is spread across quite a few folders on your Hard Drive. But the main want you would delete if you needed to recover space would be the audio libraries and loops. That would cut Logic down to about 2-3GB total.
Look in Users/Yourname/Library/Application Support/Logic and Users/Yourname/Library/Application Support/Garageband
Bear in mind Logic 8 samples will be in there too. Most of the samples are the same between them so if you still want to use L8 at some point leave it.
As for the Logic 9 icon, the short answer is a shortcut, the long answer goes like this...
User Space is where everything that is account specific goes, apps preferences, your desktop settings etc etc. This is why you can see Logic 9 in your dock, becasue the shortcut to Logic 9 is in your User space on the migrated account, but not the actual app. Apps and the applications folder is not in userspace. New Migration Wizard takes a few things from System space, but beacause there is only one system, when it is copied it copies to all accounts. It didn't take Logic 9, probably because you didn't select it in your list of Applications. You may want to try and remigrate the app.
Bear in mind that you always have to reactivate (enter your key) into Logic when you migrate as your system ID is different. If you havent got your key for Logic 9 you're stuck on the older Mac.
wow now I'm even more confused. First I can't even find the path you suggested in the finder window, I can't even see my name. Second i thought i select all the options offered by Migration before starting the process. Quick question, does it mean now i have some applications installed twice on the new mac in both new and old user account?
ps. What if when i start the logic 9 i copy the registration key when it's about to launch it and use it to reinstall it?
ps. I thought when my friend installed 9 that 8 would dissappeared or overwritten by an upgrade, does that mean that 80 GB of HD are taken by both logics?
Thanks for your time!
I think I made also a copy of everything with carbon copy clooner, would that be better?
Your name is the name of your old account. If you look to the bar on the side of any finder window while logged in it will tell you the folder name. It's the one with the house icon next to it. Swap "yourname" for that in the line of text I gave you then hit Go... in your finder's top bar > Go and paste it there. If it's empty then it was never copied.
This makes sense because Logic 8 and Logic 9 libraries are practically identical and are stored in the same place, you're actually overwriting 99% of the files with exact copies of themselves when updating from 8 to 9 because 9 has the same stuff. That's why you haven't used 80GB either.
You could but I do believe some of the keys are replaced with stars (I'm writing on my phone atm).
Using CCC would be a much easier option as I suspect logic 9 hasn't copied across for whatever reason, and in doing so, your logic 8 library, which would have been marked as part of L9 after installing that on your old machine would have lost the bulk of it's EXS instruments etc because L9 didn't cone across.
Again, you will probably have to re-enter the key after writing the new image onto your HD.
Oh and you wont have duplicate apps, nearly all apps install to the Applications folder, the migrated copies might have written over your new apps though giving you older versions. It's the libraries, preferences and bom files (which lists all the files that for example Logic may have spread across both your user space (account) and the system in case your Mac needs to migrate or uninstall them.
In the future if you migrate you need to look more closely at what you decide to bring. Only bring what you really need, for all I know your migration could have run out of copying space halfway through or had some kind of fault or error.