[size=large]Reverse engineering and then selling a product using the knowledge thus gained may or may not be ethical depending on the circumstances. In most cases however it's legal. The ethical use of reverse engineering is basic to the advancement of the art and we neither apologize for doing it nor do we expect competitors to do so.
Software is usually protected by common law copyright, and protection is strengthened by registration. In general, to copy and then sell it comprises theft of IP.
The function of a product is often covered by a "utility patent". If it is, to copy and then sell it comprises theft of IP.
The "look and feel" of a product is often protected by a "design patent". If it is, to copy and then sell it is theft of IP.
In a few cases the "look and feel" is so distinctive and so closely identified in the market with a particular manufacturer's product, that it may be regarded as a common law trademark. If people are buying a knockoff product believing on the basis of "look and feel" that they are getting the real thing, the customer has been defrauded and de facto trademark infringement has occurred.
Then there's things that everyone recognizes as a trademark, for example the names "Teknetics" in connection with metal detectors and "T2" in connection with Teknetics de jure or de facto trademarking. Those automatically have common law protection, and registration of such trademarks improves their enforceability. Their unauthorized use comprises theft of property, and in addition comprises fraud committed against the customer.
The distribution of products is often governed by commercial contracts, hence the phrase "authorized dealer". In general, the end customer is not a party to the contract and has committed no offense by purchasing the product outside the chain of authorized distribution. However the end customer often thereby forfeits certain benefits that may accrue from the use of authorized distribution, for example in relation to warranties. In addition, if counterfeit products exist, the risk of purchasing a counterfeit product via authorized distribution is virtually zero. Therefore if an end user desires the benefits of purchasing through authorized distribution, it is the responsibility of that end user to determine that the seller is part of the authorized distribution chain. In most cases the circumstances will make it fairly obvious whether or not a seller is so authorized. If there is doubt, the prospective buyer can inquire from a reliable source (for example the manufacturer or a website known to be under contract with the manufacturer) whether or not a seller is an authorized dealer.[/size]