SIMH

SIMH was based on a much older systems emulator called MIMIC, which was written in the late 1960s at Applied Data Research.^[1] SIMH was started in 1993 with the purpose of preserving minicomputer hardware and software that was fading into obscurity.^[1]

In May 2022, the MIT License of SIMH version 4 on GitHub was unilaterally modified by a contributor to make it no longer free software, by adding a clause that revokes the right to use any subsequent revisions of the software containing their contributions if modifications that "influence the behaviour of the disk access activities" are made.^[3] As of 27 May 2022, Supnik no longer endorses version 4 on his official website for SIMH due to these changes, only recognizing the "classic" version 3.x releases.^[4]

On 3 June 2022, the last revision of SIMH not subject to this clause (licensed under BSD licenses and the MIT License) was forked by the group Open SIMH, with a new governance model and steering group that includes Supnik and others. The Open SIMH group cited that a "situation" had arisen in the project that compromised its principles.^[5]

SIMH emulates hardware from the following companies.