As it turns out, there are as many origin stories for barbecue as there are spellings of the word on neon signs. These explanations range from a linguistic attempt to connect barbecue to boucan (also French) to a tall tale tracing barbecue to a Texas rancher who happened to brand the initials B.Q. on his livestock.
Patent protection usually ends when the patent expires. Here are the expiration dates: For all utility patents filed before June 8, 1995, the patent term is 20 years from date of filing, or 17 years from date of issuance, whichever period is longer.
Re: After Provisional Patent Expires... Remember provisional patent applications are not published so just filing a provisional applicaiton will not be enough to prevent others from also patenting the idea (this is what legalzoom is implying).