I've always used madplay to play internet streams on my router, but it is very sensitive to internet gaps, also madplay does not have any buffer, a better alternative is mpg123
You might look at MPD as an option, though I dont think it's an OpenWRT package.
I'm not an expert on it, just a user thru the excellent Moode streaming package. http://moodeaudio.com (Moode is a standalone RPi based music player/radio streamer, forked off Volumino) Has many features, adjustable buffering, etc. Think its command line only? But, as I mentioned, if it's not "packageized" for OpenWrt, uh, you'd have some work ahead of you.