I personally don't love this decision of where to store the files, even though it's the most logical place to put them from the programming point of view.
The primary issue is that /Library is NOT a place that I expect to find work that I've done and that can be lost if I made a mistake. For example, when I move my development work to another machine, I just move /Users/tom and I'm done. I quite often just want to wipe and re-install my operating system even!
The secondary issue is that this means that all users on a system must share the same DMXIS code. This isn't just hypothetical, my assistant and I share the same laptop which he prepares for shows, and I will often have a different version of my software in development compared with "production".
There's a tertiary issue that having your user code in the same directories as the "secret" internal files that make up DMXIS and Python encourage you to "accidentally" make changes to those files too - and then be surprised when your code doesn't work in a "virgin" installation of DMXIS. You should always keep files you can edit as far away as possible from files you can't edit.
My suggestion? Have the user code in a different hierarchy than ENTTEC's code, which would remain in /Library. Allow the user to set, somehow, the location of this user code - but have the default location for it be in /Users/$USER/Documents/ENTTEC/, which will be fine for 99% of developers.