In fact as it is, strictly speaking, illegal to publish ANY data gained from illegally tapping licenced transmissions, no specific restrictions are necessary.
Quite correct. However the law is one thing, and custom and practice is another. Publishing live data, screenshots, etc, is likely to attract unwanted attention, whereas I've never heard of anyone encountering problems as a consequence of putting delayed data on the web.
I'm not so sure about that Dave. I've had a look into things in the UK - albeit a bit superficially - and conclude that the whole area is so "grey" in terms of the various bodies involved and the courses of action open to them, that the actions of a handful of "plane-spotters" are not life-threatening - and are extremely unlikely to result in any prosecutions.
This 5minute delay business originated in the States and relates as much as anything to the Sale, not security, of data by the FAA. Airnav are stuck with a 5 minute delay imposed by the USA and therefore would have continuity difficulties if Europe was real-time.
No doubt this will attract some comments!! Ah well.