Why would I gamble with the language of "you may not be considered a trader" just to put out a free app when it comes to fines or other legal action? I'm a software engineer, you could argue that a free project is still inside of my profession.
Fines from who?
This is total FUD
It's readily provable on your part if you are putting out a free app and making no money off of it (not showing any intent to commercialize it)
The Trader self assessment bullet points are refreshingly clear and easy to interpret