The answer depends on what images you download.
The original image sets are typical in Bq/ml (for most DICOM files), but somewhat arbitrarily scaled for the HR+, HRRT, and some of the older Philips and GE scanners. Of the "pre-process" image sets, or which there are four, the 3rd and 4th sets are scaled to cerebellar gray matter, and hence can be considered SUVR images, which are unitless. Please e-mail me directly at koeppe@umich.edu with any followup questions.