Nisha did this as well
; it is known as "submissive urination". Don't worry he will grow out of it
We have concrete floors, so cleaning up wasn't as big of an issue; thank goodness!
In the mean time....don't let people pet him unless he is VERY calm. Eventually he will learn not to get excited when people walk by (they don't pet him, so why would he care?). Our trainer told us to tell people "sure you can pet my dog...just don't talk" Nisha wasn't as bad as Gary though.
I can't remember when Nisha stopped; I just noticed one day that she doesn't pee anymore! I would say, give it a few more months and he will grow out of it! Good luck!