That's why I said, "legally" lol.

A lot of frame designs are also supposed to be proprietary (BMC, Colnago, Pinarello, Specialized, you name it) but counterfeits often appear. It's possible the counterfeiters reverse engineered an actual bike..but more likely, the molds or schematic that were supposed to be kept in-house were released, on purpose or accidentally.. and that is probably why counterfeit bike frames exist, also.. the design is often different in some details because the molds could have been altered for easier manufacturing or they were a an earlier mold/prototype.