ok, found the very strange reason why it didn't work.
Before editing the shadow4 skin directly I tried the script in my skin. Of course it didn't work correctly since the call for the script in weather.xml goes out to the shadow4 skin lua file (I only noticed that later). So I removed the not working "calendar" in the skin settings from the active calendars and added the shadow4 weather calendar.
But for some strange reason Rainlendar still used the weather.lua from my skin. So no matter what I changed, it always used the wrong weather.lua file. Very strange why Rainlendar would do that and I'm very annoyed that I spent two hours or so figuring out what goes wrong in the script only to find that Rainlendar used the wrong one
Maybe the log needs to track down the path of the script used from skins, too.
Also it is strange that even though I changed the url of the Shadow4 Weather skin but it used the wrong lua file....

SORRY, my fault.

Firefox renamed the Skin file to Shadow4.r2skin-addon(2).

Rainlendar does not know a skin with this name. Renaming the file solved the problem. Everything works as aspected now.

BTW, wouldn't it be better to store the skin name in the skin file and check for it there ?

The scripts are always global. This means that if two script files have a function with the same name the one which is loaded later will overwrite the first one (or so I suspect; I haven't actually tried this). So, when modifying the scripts the function names should be changed too (that's the reason why they are usually prefixed with the skin name). Also note that the scripts are always loaded if you are using at least one window from the given skin even if that window wouldn't use any of the scripts.

It might be useful (and probably more logical too) to limit the scripts only for the skin where they are defined but it would require a rewrite of all the scripting related code.

BTW, wouldn't it be better to store the skin name in the skin file and check for it there ?
Yes

I hadn't thought about the problem of having multiple skin addons for the same skin. I'll try to do something about it.

Hi!

I can't drop the addon file over the calendar (I think because of kde4) Are there any other way to install the addon?

Thanks
Tsab

You can use the command line too:

./rainlendar2 -i Shadow4.r2skin-addon