I just found a link to Tomato for (WNDR3800) which would make it compatible with WNDR3700 and many other routers based on that reference design. These are Atheros 7161-based routers. They are made by virtually all the major manufacturers.
I had found it hard to believe, but the WebSite appears to be a Netgear-sponsored legit site. The SourceCode is at the "Download" section under "Tomato (3800)".
Has anyone looked at the code of Tomato for WNDR3800?