Yes, and no.
From a gas-emissions standpoint, they are pretty safe to use inside. It would be no different than burning a propane range in your RV. Since they're not meant to be installed inside, however, you will want to be cautious in your use of them. Heat output could be great enough to melt or burn curtains, countertops, or other nearby items. On top of that, you run the risk of someone knocking over a freestanding stove, or knocking a tabletop stove off the counter. Assuming nothing catastrophic goes wrong, however, these stoves should, in theory, be safe to use inside a dwelling. I wouldn't recommend it, though.