I tried a few more google queries and finally hit something that looks somewhat promising, albeit with links to Chinese download pages with no English README or anything. Since these things seem to be made by a dozen different manufacturers and there seem to be multiple hardware designs, I'm hesitant flash just anything, but I'll try reading through that long-ish thread to see if there's any way to figure out the model number, or if anyone's made progress flashing OpenWRT or anything else onto one of these.