FWIW -
As one who has a small handful of apps published at Autodesk Exchange, I completely agree that Free should mean Free, with no strings... While only one of my 'live' apps are Free at this time (I have several others coming), the rest of my apps are still only $1.00 at this point (of which I only see +/- $0.60 after PayPal's cut).
The issue being noted in the OP could have been easily mitigated, had the app developer instead simply selected the Trial option, instead of Free... If you've not already done so, you might consider sending them an email about this.
Cheers