This is a list of features in v56 (Dec 2017) corresponding to v54 updates at
https://gitlab.mpcdf.mpg.de/aws/galpropand of the features which are missing or not the latest.
Y= in v56 as in v54 update (not always latest)
N= not in v56
Y accurate propagation scheme
Y polarized synchrotron (but not latest version)
Y free-free emission and absorption
N new convection model (continuous at z=0)
N anisotropic diffusion
Y primary positrons
N free-escape boundary conditions
N new hadronic gamma-ray production models
N new injection spectral breaks
Y upwards compatible with latest HEALPix
Y improved HEALPix skymap format
N deuterium production by pp fusion
N Jansson and Farrar 2012 B-field
N hadronic energy losses for p and He
Basically only v54 changes up to end of 2012 are included so "Y" does necessarily imply the latest version.
v54 updates in v56 source can be found using "grep AWS2011" *cc and "grep AWS2012" *cc.