You can see what version of defMON you have by looking in the status bar when the program starts up. The version numbers are essentially just date stamps that reflect the day when the program was compiled.
If you got a version of defMON that is not available on this page, feel very free to add it here. Especially if you have an older version than the ones available here, as many of the older versions are lost.
Note that this version is for NTSC computers only. It is highly experimental and may not work at all.
For reference: If SHIFT+N is pressed in the sequence list, defMON will copy the current sequence (the one that the cursor currently points at in the sequence list) to the Next empty sequence. If SHIFT+U is pressed in the sequence list, the current sequence will be copied to the next sequence that is Unused in the sequence list (no matter if this sequence is actually empty or not!).
The hardware sync interface is available from Scannerboy at the chipmusic.org forum, right here.
The first publicly available version of defMON was the one that was “cracked” by Genesis Project in 2013. You can find it on CSDb. That version differs in some ways from the “ordinary” versions used by people like Goto80, Ilkke, and others.
The first versions of defMON that were actually useable appeared around spring 2008. At that point defMON wasn't released to the public, but mainly used by Goto80 and a few others. Many of those old versions are lost in time, but the following zip archive contains four different old versions that were dug up from the prehistoric era.
One is from April 2008. One is from a disk labelled October 2008, but I am not sure if that means that this version was created then, or if it is just the tunes that was on the disk. At least it is not newer than that. The other two I don't know, but they should both be pre 2009 too.
I remember when Goto80 tried defMON for the first time, and exclaimed “Man.. I gotta quit my job!”. :D