Originally Posted by denverd0n
In the U.S. it is pretty simple. If you require payment from people that you take on board (whether you call it a "contribution" or "sharing" or whatever else) then you are operating commercially and must have all the appropriate licenses, insurance, certifications, and so forth. If you ask people to share expenses, but will take them on board even if they do not make such a contribution, then you are not operating commercially.
This is a true statement because you added the word "require"
see 46 US Code (USC) 2101, 46 Code of Federal Regulations (CFR) 175.400
or click on this link at look at the right hand panel under "Consideration." "Suggesting"
is not "Requiring."
It is generally accepted in my cruising community (perhaps not in your cruising community) that as a courtesy strangers who "volunteer" to crew on a boat will make a contribution to the operation of the vessel. the contribution is normally stated as a "not to exceed" amount, not a per diem price. We go food shopping and split the bill among everyone on board. Sometimes a crew member will buy a tank of gas or diesel as a thank you.
But it is incorrect to assert that any payment to the operation of a vessel makes it "commercial venture." Of course this is the rule for US Flag vessels, other countries have different definitions.
By the way, it is also generally accepted in my cruising community than when invited to dinner you bring a bottle of wine. We call this common courtesy.