To be contrary, he is giving you credit and a link for the view. From a Google Search perspective, you are getting two references for every view of that page. Unless you're getting paid by the view and these SWF views don't count or you have some personal reason, I'd leave it alone. You can spend a lot of time and energy trying to do something that may, ultimately, hurt your popularity in Google. As long as you have good meta-tags and good referrers, the spiders will find you more often this way and boost your search order placement.
Giving credit and stealing are two different things.
1) He didn't get authorization to steal the use of the result. he is not using his bandwidth to do it, he is using the OP's bandwidth..
A lot of sites don't want you embedding their content. Think MP3's, Images etc...
Not only did the OP pay for the weather station and its upkeep, but he also paid for the software, pays for his hosting and his time. The offender is not assisting with any of that, just stealing data so his website has cool stuff on it.
He has apparently also been asked to stop.
2) Hotlink protection which is normally thought of for images can be done for just about any content and if done correctly is trivial to setup.
The OP has mentioned that he has made several .htaccess changes, but I suspect he is trying to block the offenders site, not prevent hotlinking.
Or fix your page up even more so that there is no question where the data is coming from.
And how does he do that? The Offender is not showing the OP's website, only his objects. Where are you going to put more info in the object (the SWF) that provides more details of where it is coming from?
It already has across the top of it "Real-Time data from the RNSYC weather station".