I am looking for a *.mp4 decoder to use with bsplayer. The 3ivx codec allowed me to do this but it has expired. Is there any other decoder out there for this?

3ivx decoder doesn't expire. Only its audio en/decoder does expire. Grab yourself a copy of CoreAAC for audio decoding, and adjust 3ivx splitter's setting to "allow unsupported decoders" and uninstall the 3ivx audio filters using Radlight Filter Manager or by hand.

Thanks I'll give it a shot.

latexxx is right for audio use coreaac

for video you can use any decoder you want: 3ivx, ffdshow, xvid, divx5...

3ivx splitter is still pretty mandatory.