Looking at it more closely, I think the windguru code is going to be a problem. I’m not sure how to go about it, or if it’s even possible.
You are allowed to show forecasts for up to 10 different spots per website (domain)
But I’m sure if it is possible that the solution would be complicated.
Why not try the first two - windfinder and meteobkue - first and see how you get on with those.
EDIT
It looks like the easier approach for windguru would be to link to the site using links generated from this page:
http://www.windguru.cz/int/link.php