A few years ago landing at Boston KBOS we were transferred late to tower. Couldn't get a word in edgeways on the radio. At about 100 feet there was traffic just about to get airborne on the parallel runway. We thought about going around but landed. Tower just said "thank you xxxxx Contact ground". We took the thank you to be implied approval of our actions. I know we were incorrect to continue and land without clearance but an unnecessary goaround when the runway is clear and there is proximate airborne traffic is not desirable either. They often clear us to land there when the runway is occupied anyway.