An 'experimental' beta build is now avaible, for each OS (,MacOSX, Linux and Windows), as an offline installer in the "GAME GOODIES" section.
At that day : 0.16.24 version
Thank you for this note.
Don't install this into your regular gog directory unless you disable auto update - GOG galaxy will reset to last known version after launch otherwise
edit: experimental beta branch on GOG also has this version for some time now (stating it is 15 days old as of today = 6th March)