Just like I love piCal, I think xoopsgallery rocks!
my .25 cents,
Gnik
Did you ever try Agendax?
Like you said... back to the topic at hand. I took a look at the mod and found a couple of things: It looks like something I can put into XoopsGallery. It's not a permenant mark--it adds it as the pic is being pulled from the server, so it is trivial to work around. It's also using gd2 which I know little about (and why use that instead of NetPBM or ImageMagick that is already required by XoopsGallery--not that I know much about them either).
It is an interesting idea, but I'm not sure that the patch in it's current form would do what you really need. It might be better off hooked through the preprocess routine when an image is added to the gallery--then it would be permenant (and won't require being run every time the image is called, so it's better for busier sites). I'm going to stop short of saying anything definate, but I'll take a look.