can i give someone my old version of OS

Hi,

my friend has an issue while installing Sierra.

Can i possibly give him my older version of El Capitan (which i downloaded from Purchased from App store) without any problems? (After installing El Cap. he wants to upgrade it to Sierra)

The OS is not somehow connected with my Apple ID, isn't it? So it could possibly work for him without affecting my Mac, right? Or can it somehow affect my current and other upgrades to new macOS versions?

Thanks for answers in advance