As seen in the last comments there seem to be issues with more recent kernels and the current tarball although it compiles without issues. I just uploaded an updated tarball which should take care of this. Big thanks to Sergey I'linykh who provided a patch for this.
As usual you can get it here.
Discussion
udp packets appear as new to iptables, not as related. Would it be posible to have an updated version for kernel 3.14? Thanks!!
I no longer have the infrastructure do do any development on it. It appears that something in the more recent kernel versions changed and therfore the modules are just broken.
Sorry that I can't help you with that.
My pay per view IPTV service is based on this combination (RTSP / NAT) and without NAT properly working I can only use a single set-top box (I DNAT the incoming stream to one STB). Thanks again.
Latest version compile but is not working with kernel 3.16 for example. :-(