Gallery + ??? forum

New to gallery.

I've been given the task of putting my school's photo library online. We have something like 200,000 images spanning 40 years.

Gallery has a bunch of features I like:
* Fine grained permissions control
* Symlinks
* Nested albums
* Multiple resolutions
* Watermarks.
It goes on.

I would like to integrate G with some form of forum software.
Here's my thinking:

I didn't take all the pictures. Probably only 10% or so of them. Even with those my memory will be faulty. So I want to be able to use the collective memory of our alumni and ex-staff.

For each Album I would like to have a Forum. Within each Forum I'd like a (potential) thread for each image in the album, PLUS a few other standard threads.

Suppose I use a time based criteria for the overall album organization.

1984 has a subalbum Methye_Portage_Canoe_Trip

Now MPCT has an associated forum with it.
The images have a unique ID.
I use the custom field modulul to have a field called "Who" with default value "????"
Every image has a link to the thread in the associated forum corresponding to that image. Here they can start stories about the trip, talk about the people in the pictures and so on. The thread starter has a back link to the picture.

I also distinguish between the Caption and the Description fields. Description is what you'd expect of 'described video' Caption is it's relevance to the rest of the set of pcitures, to events that happened. So Description may be: "Mr. Nordahl's canoe going broadside into a large rock at the bottom of Brassy Rapids" while the caption may read, "The fates finally caught up with Mr. N. Boasts about skill in running rapids finally came a cropper. Adding insult to injury: Mr. B got it all on film, so there won't be later denials!" Forums are where candidate captions can come forward.

Ideally too, the forum supports threads. Alumni will read this in fits and spurts. So timeline view is not always the best view. They need to be able to respond to a particular message in a thread. But also they need to see what's new.

Which forum package goes well with gallery and meets these needs? My site will be hosted on Dreamhost.com on a Linux server, so windows packages need not apply.

I took a quick look at geeklog. But I didn't see much in the way of pix at all.

To make clear: My application focus is tens of thousands of images, organized in hundreds of albums.
Each Album has a forum. Each photo has a thread in that forum.

I want users to be able to use the photographs and the albums as springboards for discussion.

I am NOT looking for a blogging package.