Well, it is hardware that runs reliably every day in civil applications (like what we're doing, communicating on the web and all that). The rooms on board of the ship that hold the server bank are shielded against EMP, so I don't see any problem there either.
And of course that stuff is cheaper than proprietary military hardware that is tailor made for one single application.
well for one thing look at how the STUXNET virus got into the Iranian enrichment facility, by using the fact that the facility used off the shelf parts for the computer system. It makes male-ware that much easier to attack, and the last thing you want is the blue screen of death at 50,000 ft. Also it has been known that the CIA, other government agencies, and other countries have put viruses and built in backdoors into commercial hardware and let it be bought up, then they take control of it as needed.
As for the aircraft, as pointed out easier sure they got the shaping, anyone who has three pics of the f-35 at different angles can make a exact copy of the thing (on the outside) but the engines show the lack of advanced jet know how. At best guess the thrust of the two engines varies from 10,000 lbs less than the single engine of the f-35, to only slightly more, that shows the Chinese a long ways to go on even the basic development side even when trying to copy other countries stuff, not the least in actually innovating their own stuff.
Lastly one earlier poster noted that this aircraft would probably be for the navy since the navy doesn't have any 5th gen fighters. I want to point out that there is speculation that the j-20 will be used on future Chinese aircraft carriers, also the j-20 is thought to be more of a strike aircraft like the Su-24 or even more accurately a flexible large jet aircraft like the F-111 which was used in a variety of roles. The j-20 is huge and would probably not be very good in a dogfight.