dcmo5 is an open source MO5 emulator by Daniel Coulom. It uses SDL for video and sound, so it can run easily on many platforms.

This emulator is not actively developed anymore, as Daniel is now working on dcmoto. Unfortunately, dcmoto is not open source and the GUI is windows-only.

The dcmo5 homepage makes a good job at showing what it does. Here is an (incomplete) list of things it doesn't do right:

• The color palette is wrong. dcmo5 uses the TO7/70 palette which is quite different. Whatch out for this! There is a version with a more correct color palette here: https://github.com/pulkomandy/dcmo5
• The gate array registers are not completely emulated
• The tape drive isn't correctly emulated. Access to the tape are short circuited and the emulator pokes the K5/K7 file directly in RAM. This may not work with programs using fast-loading techniques. To avoid the issue, tape image of fast-loaded programs are modified to work in DCMO5. They use undocumented 6809 opcodes, which the emulator will intercept to trigger various actions related to file loading. Of course, such image files can't work on real hardware.

Here is a quick howto for dcmo5

• The “Options > Parametres” menu can be used to change the language (first field). This is useful if you ever get stuck in French mode.
• The emulator is a bit faster when using 1x zoom. However, showing most of the settings windows need 2x zoom.
• The MO5 has an AZERTY keyboard. You can remap keys using the keymap preferences if your computer is QWERTY or something else.
• There is no directory browser, all software must be in the “software” folder in the dcmo5 executable directory (the GUI code from dcto8d should be imported to fix that).
• K5 files in the software folder must have the K7 extension. Using K7 for MO5 files is confusing and should be avoided (K5=MO5 tape, K7=TO7 tape), but the emulator was not updated to reflect this.

You are now ready to run programs.