Well, open source is open source.
Here is one:
A double walled chimney stove:
Outside: Cone shaped removble sheathing. Holes top and bottom, air inlet and exhaust.
Inside: "W" shaped water container, possibly rounded at bottom, hole in center
Lid: Hole in center
Stamped processes for all pieces. Assembly, none...sell the pieces.
Heat source: any... wood, alcohol, canister, WG, kero...
Advantage: Heats the inside and outside of the water.
Patents: I don't think this is patentable, not a new idea nor significant improvement, just not usually thought of.