Don't know about ready availability or free availability, can be purchased through FPS and Franz Singer in Germany.
Though the machines were built to a standard and have many similarities, each machine is unique, there were revisions over time-mostly to the control. Would suggest it is very very important that you get the "orange books" (documentation) when purchasing the machine.
There are 2 binders plus a bound book . One binder is a user manual and explains general layout/functions of the machine and very detailed info on how to run the control. The other book has detailed electrical schematics and prints, and includes notes in German on adjusting various electrical parameters and troubleshooting the control electronics. The bound book has mechanical drawings including part numbers of the major assemblies, including the spindles.