Post the link to the carb cleaning video you referenced. It'll give us a better idea of what was and wasn't done.
http://www.ex-500.com/wiki/index.php...uretor_Refresh is for the slightly different carb model used on the 500, but you should have done basically those same steps.
The leak is coming from the bowl seam. This indicates a problem with the O-ring. It could be damaged, but it's likely old and worn. That also is a clue that other rubber parts, like the float needles, are worn and need to be replaced too. The rubber parts degrade over time and need to be replaced, simple as that.
Did you just use the bottle of liquid SeaFoam? The aerosol spray carb cleaner frequently doesn't have enough pressure to ensure all the little passages are clean. Actual compressed air is recommended. If you just poured liquid into it, I doubt it did much of anything.
Also, Sea Foam is a fuel treatment, not carb cleaner. For cleaning up gummed carbs, they suggest up to a 1:1 ratio and letting it sit in the carbs for up to 3 days. It takes a lot of Sea Foam to actually clean things up.