afni.nimh.nih.gov

It's included in the source on github (https://github.com/afni/afni/tree/master/src/matlab) or on this site here. I'll say that it hasn't been updated in quite a while. You could also convert any AFNI dataset to NIFTI and then use functions in Matlab for importing those NIFTI files. Though the AFNI Matlab tools still worked the last time I tried them.