Editing Hercules (emulator) (section)

==Operating systems status==
Hercules is technically compatible with all IBM mainframe operating systems, even older versions which no longer run on newer mainframes. However, many mainframe operating systems require vendor licenses to run legally. Newer licensed operating systems, such as [[OS/390]], [[z/OS]], [[VSE (operating system)|VSE/ESA]], [[VSE (operating system)|z/VSE]], [[VM/ESA]], [[z/VM]], [[TPF/ESA]], and [[z/TPF]] are technically compatible but cannot legally run on the Hercules emulator except in very limited circumstances{{citation needed|date=January 2017}}, and they must always be licensed from IBM. IBM's [[Coupling Facility]] control code, which enables [[Parallel Sysplex]], and [[UTS (Mainframe UNIX)|UTS]] also require licenses to run.

Operating systems which may legally be run, without license costs, on Hercules include:
* Older IBM operating systems including [[OS/360]], [[DOS/360]], [[DOS/VS]], [[MVS]], [[VM/370]], and [[TSS/360|TSS/370]] which are either [[public domain]] or "copyrighted software provided without charge."<ref>{{citation | contribution-url = http://www.hercules-390.eu/hercfaq.html#2.02 | contribution = 2.02. What operating systems can I run legally? | publisher = Hercules 390 Version 3 | place = EU | title = Frequently-Asked Questions}}.</ref>
* The [[MUSIC/SP]] operating system may be available for educational and demonstration purposes upon request to its copyright holder, [[McGill University]]. Some of MUSIC/SP's features, notably networking, require z/VM (and thus an IBM license). However, a complete demonstration version of MUSIC/SP, packaged with the alternative Sim390 mainframe emulator, is available.
* The [[Michigan Terminal System]] (MTS) version 6.0A has been tailored to run under Hercules.<ref>{{cite web | title = Michigan Terminal System Archive | url = http://archive.michigan-terminal-system.org/ | access-date = 10 December 2022 | archive-date = 11 January 2011 | archive-url = https://web.archive.org/web/20110111201148/http://archive.michigan-terminal-system.org/ | url-status = dead }}</ref>
* There is no known legal restriction to running [[open-source software|open-source]] operating systems [[Linux on IBM Z]] and [[OpenSolaris for System z]] on the Hercules emulator. They run well on Hercules, and many Linux on IBM Z developers{{who|date=April 2022}} do their work using Hercules. Several distributors provide 64-bit z/Architecture versions of Linux, and some also provide [[ESA/390]]-compatible versions. Mainframe Linux distributions include [[SUSE Linux Enterprise Server]], [[Red Hat Enterprise Linux]], [[Debian]], [[CentOS]], and [[Slackware]]. Sine Nomine Associates brought OpenSolaris to System z, relying on features provided by z/VM. Emulation of those specific z/VM features for OpenSolaris is included starting with Hercules Version 3.07.
* Certain unencumbered editors and utilities which can run on a mainframe without a parent operating system may be available to run on Hercules as well.
[[File:Hercules IPL of IBM ESA-390 hardware emulation running Debian GNU-Linux.png|thumb|Debian GNU/Linux running on Hercules]]
* PDOS/3X0 (Public Domain Operating System, mainframe version)