I am moving into a new house and the floors are almost 100 years old. at one point they were finished with some kind of varnish or lacquer and is mostly worn off in the high traffic areas, and pretty thin in the other areas.

I am not allowed to sand the floor, but is there some way to breath a little life into them so they don't look so dry and dusty?

maybe an oil, i would rather not have some synthetic harsh smelling chemical. we have enough trouble trying to get rid of the cigarette and incense smell as it is.

You can try something like a tung oil or Danish oil .It wont do much but will seal up the floor a bit and wont smell very bad. Places like Home Depot don't usually have a good selection of oil products but Wood Craft and pro paint supply stores usually do.