Hm, in general there is just an option to specify a minimum Jmp version.
max version will be available in Jmp 18:
Add-in template to include Maximum JMP Version allowed
So, if this message pops up, somebody seems to be sure that there will be an issue in Jmp 17.
If you need just part of the code, you could rename the file to .zip and extract it.
Then either the code can be found in the jmpcust file - or as individual .jsl files.
Or you could ask the author ...