In BikeCAD, Fork length is measured from the axle to the crown in a line parallel to the steerer tube. BikeCAD also provides another fork measurement which is the direct distance from the axle to the crown.
Be aware that while BikeCAD defines the fork length as being the measurement taken parallel to the steerer tube and uses the term axle to crown to refer to the direct distance between the axle and the crown, this is not a universal standard. You should always be careful to double check how your fork is measured when modeling it in BikeCAD.