I think the pro version and charging stuff is totally fine. It's the lack of transparency that bothers people. I shouldn't have to figure out their profit model from HN comments. If you want to be paid for your work, charge for the whole library or make the free/pro distinction very clear to people. Don't try to hook them in with a free offering while locking features behind a paywall that they discover later.

Or if you want to be altruistic (as you keep referring to nonprofit) make it free and solicit donations/patreon.

The current approach is certainly a new one and I am interested to see if it pays off.