You can buy your friends FCP and he needs to give you the licence. However he is then no longer the license holder so he should uninstall the software.
If he continued to use the software after giving up the license he is then technically running the software illegally.
You should be able to get upgrades as long as they are available.
Here is the paragraph from the Apple License:
”
3. Transfer. You may not rent, lease, lend or sublicense the Apple Software. You may, however, make a one-time permanent transfer of all of your license rights to the Apple Software to another party, provided that: (a) the transfer must include all of the Apple Software, including all its component parts, original media, printed materials and this License; (b) you do not retain any copies of the Apple Software, full or partial, including copies stored on a computer or other storage device; and (c) the party receiving the Apple Software reads and agrees to accept the terms and conditions of this License. All components of the Apple Software are provided as part of a bundle and may not be separated from the bundle and distributed as standalone applications.
best wishes
Neil
http://www.patience.tv