Legally, yes. The Magnuson-Moss Warranty Act (US) says you can repair your own device, but using unofficial software like ST 5510 gives Canon legal grounds to deny service.
No. This is strictly a Windows tool. Mac users must use VirtualBox or Boot Camp to run Windows. Canon Service Tool St 5510 Free Download
: Identify root causes of performance issues and monitor overall printer health. Important Warning: "Free" Downloads Legally, yes