Tokyo Marui does not seem to care who copies their Gearbox design, and instead has only targeted people who attempt to pass off their airsoft guns as non-clones of TM.
Additionally, even if TM had a patent on the Version 2 gearbox (for one example), due to the initial selling of the Ver2 rifles starting in 1992, its already expired.
Once patents expire, or when someone is not willing to legally protect their intellectual property, such as what TM has over all done, your right to "your" property is lost legally. Cybergun is just protecting their property that they licensed from firearm manufacturers such as FN to be able to market them legally.
They are doing what they must do to legally to protect themselves, but I guess this is being mean capitalistic pigs don't you think so?