About ten years ago I saw a currently manufactured cargo biplane, or perhaps about a 10-seater passenger plane that was not used for passengers?? I think I was told that it was of Polish manufacture, that it was not US-certified to carry passengers, maybe not certified to carry freight for hire either. I think the reason pertained to the OEM parts not meeting current US standards. Unfortunately, I cannot remember how many engines/propellers.

I remember my pilot-friend telling me its cost, he estimated, would be about $350K while a US-certified version would be about $1.5 million.

I would recognize the aircraft were I to see photographs. It remains in memory because I was surprised that a biplane would still be manufactured for commercial use.

Is this it?
http://www.goldenruleairlines.org/2300-golden-rule-mercy.htm

John:

I looks a great deal like it. Of course, color scheme is different. Possibly the door was positioned either farther to the rear, larger/wider. Please tell me about what I'm looking at in as much detail as you care to use.

Tail dragger -- yes.
metal struts (right term??) maintaining wings - yes.
single door - yes.
fixed wheels - yes.

Beyond these details I becoming hazy. I saw the aircraft in either Port Townsend or Port Angeles, Washington's, private/small airport; I'm betting on Port Townsend. There was also an exotic propeller-driven single-wing aerobatic plane so notwworthy that my friend drew it to my attention.

Antov AN-2 Russian

Go to https://forums.accuratereloading.com/eve/forums/a/tpc/f/558107455/m/821106767 and have a look - we beat this thing [AN2] to death a couple of months ago.
Enjoy!