Bartering will not be allowed with people not in the challenge. Likewise, the exchange of labor-for-food with outside parties will not be permitted.
Salt will be allowed for preservation only. You may choose any salt you wish (sea salt, table salt, pickling salt, etc.) but it must be used in the preservation of some food article. Salt will not be permitted for 15 days before the first day of the challenge - if you catch a fish in that window you'll have to freeze it instead of salt it, if you have pickles they need to be made before that, etc.