My understanding based on the link in my sibling comment is that the current commercial systems don't inter-operate and that the diabetic must read from one device, calculate a dosage themselves, and then enter that dosage into a second device. At each of the three stages there is the potential for human error and common circumstances such as performing each task in the middle of the night while suffering the effects of sugar imbalance make errors more likely. Not that such circumstances are necessary for errors because the process is repeated by diabetics on the order of a thousand times a year over decades.
My understanding is that the issue with the device upon which OpenAPS relies is that a bad actor could possibly reprogram it over BlueTooth. Doing so would require close physical proximity to the individual. By close to the point that a bad actor could probably physically harm the individual or gain access to the insulin itself...i.e. to within a few feet.
To put it another way, one problem the with FDA approval is that OpenAPS uses a no-longer-approved device and the reasons it is no longer approved are not based on evidence of increased hypoglycemia. Their related to medical device manufacturer liability and hence the cost of insuring against risk.