You can download Midi2CV Mk2, MidiARP and MidiSEQ source code using the following links:
Midi2CV Mk2: midi2cv_mk2_112_src
MidiARP: midiarp_095a_src
MidiSEQ: midiseq_097a_src
The code can be built using WinAVR-20100110 toolchain available here: https://sourceforge.net/projects/winavr/files/WinAVR/20100110/
Have fun hacking!
MidiSizer 
Can it be that something is exchanged in the program? I can only record when the LCD shows (Stop). At Record, he plays. I have pretty much all variants through incl. PAL and GAL software. Programmed via SYX and external with eprommer.
I’m not sure I follow — MisiSEQ records when recording is active, and when it is active, it shows [stop] so you can stop recording by pressing the switch.
Is there source for MidiARP97? Interested to see how hard it is to introduce your own arp patterns. Any plans to move this to GitHUB?
MidiARP 097 source code is available here: https://midisizer.files.wordpress.com/2020/06/midiarp_097_src.zip
I’ve started moving the code to github but it takes time…