Um die Diskussion voran zu bringen werde ich mal einige englischsprachige (und andere) Leute - die bewusst nichts mit OSm am Hut haben - fragen, ob es die Dinger auch in England / USA gibt und wie man sie dort nennt.
There is nothing much like the Swiss Waldhutte in England. I guess the nearest word is cabin, which is more USA than England. Cabin suggests a wooden building somewhere in wilderness. However it is more accommodation, a private dwelling. It is not really somewhere to hold one day/night group festivities, the reason i've been to Swiss Waldhuetten. However a cabin can be either on or off the electricity network and water network, so does fit in that respect.
I've spent a short time in USA and never come across anything similar there.
Maybe try New Zealand to see if they have an English word which fits better?
Andrew