Is Decompiling Legal with forexdll? Courts in the U.S. have always upheld the right of users to know exactly what code is being installed on their systems by programs they have legitimately obtained. Legality of reverse engineering depends on the country and the purpose of decompiling. As a rough summary: In the USA, it is legal as long as the software was obtained legally, but if the license prohibits it explicitly (and most software licenses do) then it is a breach of the contract which the license constitutes — thus “illegal”, but a matter of civil law, not penal. The DMCA also has ramifications in the matter. The reason for which you do the reverse-engineering is important: if you do it in order to circumvent a system which deliberately controls access to copyrighted work, then the Law will smite you mightily. In the European Union, reverse engineering is legal as long as it is for interoperability purposes, whatever the license may say on the subject. Reverse engineering