Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Friction
FRIC_FRICParameter: Spin Friction
FRIC_SPINFRICParameter: Mass Dependence
FRIC_MASSDEPParameter: Size Dependence
FRIC_SIZEDEPParameter: On
IN_FRIC_ONParameter: Animation Time
IN_FRIC_ATIME