I understand we love our hugh, but unless he understands CODE, he would never know himself.
Kalel, let me try to calm your worries.
If it all looks like greek to you, know that several people who do understand code have poured over this and its prototypes for the last few months without any concerns.
Nowhere in this code is it actually sending out any of your sales data, and it doesn't have access to things like your password etc. It stores all data on your personal computer, and none of that sales information is being compromised.
You can't get ironclad 100% safety from anything you do online, but this is particularly transparent and pretty easy to audit for yourself. If this person wanted to be nefarious he could have created this as an application that was a total black-box (click and it works, with no idea HOW it works). That's not what has been done here.