Reverse engineering is a legally acceptable way to take an existing product, figure out how it works by breaking down the functions, and then use that information to make a similar product. The new product would be slightly different so that it would not breach the copyright of the original product, and is a common way that manufacturers keep up with selling goods that are available from other manufacturers.
Reverse engineering is legal and quite popular in the technology industry, where it is referred to as "emulation."