https://code.google.com/p/r8brain-free-src/
http://www.kvraudio.com/forum/viewtopic.php?p=5459586#5459586
Nice, but since you post in in the dev corner and I suppose you want to imply that it could be useful for OpenMPT... I suspect that the only place where it could be useful would be the sample editor. It states that it can work with any samplerate, but it probably requires some setup before every conversion, so it's not very useful for the resampler that can be found in the mixer routines.
I've been using r8brain PRO for years now.
FWIW, r8brain-free is now used in the latest revisions for arbitrary sample rate conversion in the sample editor. I still don't think it's practical for realtime mixing, though.