Today I saw that Office Depot had a DIR-615 on sale for $40.00. It was a new hardware revision: C1. I took a chance that it was a new non-Ubimax based router. I'm glad I did, at least so far.
The router is based around the Atheros AR9130 CPU. This is MIPS based, so there's a good chance that I'll be able to put FreeBSD onto it. We'll see how it goes.
I'll report more when I get a chance to examine the RAM and Flash parts, as well as map out the serial port to see what is reported there. Stay tuned.