You have to modify your theme to show the full iamge directly. All other images are processed via the GDlib which "kills" animated gifs somehow. If your server supports you may try Imagemagick instead (although I don't know if it preseverses animated gifs).
I'm also interested in displaying animated gifs.
How do I modify the above code to display full animated gifs when tagged with 'animated' in image.php? I was thinking of putting the code in the gallery codeblocks.
Currently only colorbox slideshow shows the animated gifs. I would like to have the image page itself showing the original gif image.
The GD library does not process animated GIFs, so you have to have available and enabled the Imagick library and handler. If you have not option for selecting Imagick then your server does not have support for it.
Your other option is to load the images in the exact size that would be cached for the image page. Then the image will be copied rather than resized.