a radio receiver, which includes a GPS, has to have a local oscillator as part of mixing down the high radio frequency to baseband; some have an intermediate frequency stage. The base band is then processed to extract the signal.

cheap receivers leak the local oscillator.

computers can also leak the oscillator clocks used for the processor and logic - try operating an AM receiver near a computer and see what happens. an old fashioned glass-tube CRT leaks a bunch of signals and this is how the TV detector vans in the UK work - and it would probably be so expensive to shield the TV to make it "invisible" it's easier to pay the license!

measurements of GPS *receivers* (not including any bluetooth stuff) show that they hardly leak anything and are practically undetectable it tends to be cheap FM radios and computer games that are unshielded and cause interference. CE marking and EMC has improved this situation quite a bit, but overall radio noise pollution is pretty dreadful round the world.

HTH