I agree that there is a strong resemblance between the Mac version UI of 1PW and enpass but 'shamelessly stole' are some strong words to use here.
The UI for enpass may not have any unique creativity but it isn't possible to drastically differentiate every app from all the other apps having similar functions. Some designs may be proven to be aesthetically and functionally fulfilling all goals and drawing ideas from them, while avoiding blatant plagiarism, is nothing bad at all.
On the main topic, I am truly disappointed that an otherwise excellent app, is dragging its feet so badly on being open for a security audit. After all, it is not trivial data that they are dealing with. These little things are what could turn away potential customers or deter evangelists from referring users to it.