MacOS is not copy protected in the traditional way. But that does not mean it is freely available for download using just any device. Typically, such a download requires a Mac.
if you do manage to download the Installer file, the procedure to make that Installer into a stand-alone BOOTABLE installer disk is complex, and readers have not posted reliable methods to accomplish that part on a Windows machine.
Your Mac has built-in ROM features that allow it to re-download and re-install the last-running MacOS, or if you prefer, the MacOS that it shipped with originally. You generally do not require any other computer to accomplish this.
If you have a working MacOS, what and how you download is more flexible using the full power of macOS. For most Macs that can run Catalina, if MacOS is not working properly, using Recovery is the best way forward.
How to download and install macOS - Apple Support
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