The picture below is the surface.
If you look back at week four, the last week of pictures, you can see these tan globs were quite small but clearly they are growing in size and they are quire foamy. I still don't have a good idea what this is. Here's a picture from the side so you can see what the underside of these things are. (The top of the picture is just below the surface.)
I've tried looking at pictures of different ferments (and not just beer) to get a sense of what's going on. I haven't ruled out mold but I feel confident it's actually just some weird saccharomyces fermentation. I found some pictures on a kombucha site of "bad" yeast ferments that look really close to what I have here. It's definitely not the weird pancake appearance of a kombucha scoby nor is it the jelly-textured vinegar mother of acetobacter. I read a research paper that studied Allagash's coolship beer and found that saccharomyces was fermenting as late as 3-4 months into fermentation, so that would match the timeframe for what is going on in my beer.
You can see there is no pellicle, which is unusual in my experience with sour brewing out of lab
cultures and dregs. Normally by this point there is enough oxygen seeping through the CO2 over the beer to see brett and/or bacteria form a pellicle. Nothing here. I believe the pellicle is absent because the foamy whatever-it-is is slowly pushing out CO2. Not like a vigorous fermentation but the airlock has some bubbles trapped in it (see the picture on the right) which happens when there is a slow release of gas under the airlock. That would certainly make sense with all that foam around the globs.
I'm still not brave enough to capture a taste. Maybe next month.