I wonder if there's still any real need to support both (but perhaps v5 layers on top of v4, so it makes sense to implement them in layers, and little overhead to provide both?). They have a howto-section on manually forwarding dns - but socks5 really should be enough for most applications.
While a general forwarding tool will always be able to forward dns, from a security and usability standpoint, it would seem just providing socks5 (and 5 only) might be better.
As for piping - as I mentioned it looks like there's no support built in - but it should be possible to make a wrapper. Would need something on the other end though - like a netcat that takes an output filename, and then spawns another listener and redirects to a file or something.
I'd be interested in if there's any real performance differences between openssh socks5/forwarding and this project. Especially since they build on the same primitives.
[1] https://github.com/securesocketfunneling/ssf/tree/master/src...