I am running Fedora 2.6.11 under Fedora 14 Linux.
I downloaded the exposure blend script and put it in the scripts directory and then ran refresh scripts.
I now find under Filters>Photo>Masks>
what looks like the right thing.
Am I right?
Two locations for photo (Exposure Blend). The first, as you found out, is to define masks. I never even bother touching this one. The second location is near the lower part of your Filters Menu. Once you choose this option, it will ask you to input 3 different images. Note, this is one of the few filters that doesn't require you to have an image to open or new layer open to start off with (i.e., only need to have GIMP Window open; no layer or image or anything else. It creates a new image from scratch). :)