Here is fine. To quote myself from the OP:
I don't mind public questions about, for example, how class X fits into the architectural concept design, or why I split function Y into several separate things, etc. You would have to get into extraordinary - and extraordinarily comprehensive - detail for that sort of information to meaningfully reduce the effort required to duplicate my work. Copy and pasting source code is what the NDA is really aimed at.
As for positive reasons to use Java, I know it well, it's portable, and it has a huge array of mature features and free (even for closed-source commercial applications) libraries that I can use.