The linked article hit my questions' topics but I did not deeply understand nor the configuration of the Apple ID on the fresh installed El Capitan nor the legal aspects of the solution.
This reading brought me to another solution: Alternative solution Said that, after some search, I found this macworld article showing alternative methods to upgrade from 10.5.8 MacOSX version to a more recent one. The download links for CCleaner for Mac Free can be find on the bottom of this page by press the button.
buy the DVD of Snow Leopard (10.6) from online Apple Store and install it on 10.5.8.✘ MacOSX 10.6.8 is required to be installed (due to Mac App Store introduction) on the iMac Official solution (or what I undestood reading Apple website) ✔ my iMac version is listed under the upgradable devices Now I want to upgrade my OS to El Capitan (10.11). I have an iMac(Early 2009) running Leopard (10.5.8).
