I have already sent Berry 2 test reports and have just now sent him a third - the latter about what I have termed "the Systray problem".
The symptoms are that sometimes, after being minimised/closed to the Systray, NF disappears from the Systray, though the process appears to continue.
The collage of screenshots below is intended to explain it, and what I could find out about it.

[attach]

download from http://notefrog.com/

not updated since 2015-October-11, in fact it seems you can't even buy it any more:



and if you click "go PRO...", you will get a 404:

I am pleased to report that on 2018-06-03 the NoteFrog blog seems to have come out of stasis with a post:
(Copied below sans embedded hyperlinks/images.)

NoteFrog V3 available – free for everyone.
Posted by berry – June 3, 2018
Development of NoteFrog has resumed. Until a significant upgrade (Unicode compliance – Version 4) is complete, the current version of NoteFrog is available, as is (it’s the latest production release but we will not be making additional changes to this version), for free. For now, you will require a NoteFrog registration key. A complimentary registration is available on the NoteFrog site NoteFrog registration. If you prefer a personalized registration, send a request, which contains your desired registration name and email address to HTConsulting htconsulting@gmail.com. You may download the current version of release 3 and a complimentary registration key here NoteFrog version 3.

Database encryption is available in version 3, however, an upgrade to version 4, when available, will require an unencrypted database, which is easily available from the Library Menu.