While it's important to clarify right at the start: z/OS is proprietary software owned by IBM, and there is no legal, "free" public download link for the latest versions like z/OS 2.1 or 2.5 for use on the Hercules emulator.
Could you please share the draft you'd like me to review? In the meantime, here are a few things to keep in mind:
You're looking for information on Hercules, a mainframe operating system, and its potential download links.
The core of the user's request is the operating system itself. It is vital to understand the distinction between the emulator and the operating system.
To run IBM z/OS 2.1 on the Hercules emulator, you must obtain two separate components: the emulator software and the z/OS operating system images. 1. Download the Hercules Emulator
Hercules z/OS 2.1: A Comprehensive Guide to Downloading and Installation
The emulator is open-source and can be downloaded for various platforms from its official sites: