Ah! We don't really have a defined, public interface for this. We should have. In the meantime, you can use:
import SCons print SCons.__version__
(Where, of course, you can do whatever you like with the SCons.__version__ string, not just print it.)
If you are looking to ensure a certain version of SCons, use:
EnsureSConsVersion()
You use it thusly: EnsureSConsVersion(0, 96, 93)
Credits: StevenKnight, TaybinRutkin
