Already had the Apple Developers Tools installed - maybe they're not necessary.
Installed Fink (binary installer) and Fink Commander (binary installer).
Installed X11 and X11 SDK (packages).
Used Fink Commander's preferences to allow unstable and unstable-crypto packages.
Selected pysoulseek from the list of available packages and selected Source>Run in Terminal>Install from the menu. Selected all default options. Left this running overnight.
Ran X11.
In the Applications>Customize menu, added Soulseek as /sw/bin/pysoulseek.
Ran this new menu item, then chose a new username and password from Pysoulseek's settings menu.
It worked.