partial class Examples
{
  public static Rhino.Commands.Result DivideByLengthPoints(Rhino.RhinoDoc doc)
  {
    const ObjectType filter = Rhino.DocObjects.ObjectType.Curve;
    Rhino.DocObjects.ObjRef objref;
    Rhino.Commands.Result rc = Rhino.Input.RhinoGet.GetOneObject("Select curve to divide", false, filter, out objref);
    if (rc != Rhino.Commands.Result.Success || objref == null)
      return rc;

    Rhino.Geometry.Curve crv = objref.Curve();
    if (crv == null || crv.IsShort(Rhino.RhinoMath.ZeroTolerance))
      return Rhino.Commands.Result.Failure;

    double crv_length = crv.GetLength();
    string s = string.Format("Curve length is {0:f3}. Segment length", crv_length);

    double seg_length = crv_length / 2.0;
    rc = Rhino.Input.RhinoGet.GetNumber(s, false, ref seg_length, 0, crv_length);
    if (rc != Rhino.Commands.Result.Success)
      return rc;

    Rhino.Geometry.Point3d[] points;
    crv.DivideByLength(seg_length, true, out points);
    if (points == null)
      return Rhino.Commands.Result.Failure;

    foreach (Rhino.Geometry.Point3d point in points)
      doc.Objects.AddPoint(point);

    doc.Views.Redraw();
    return Rhino.Commands.Result.Success;
  }
}

Partial Friend Class Examples
  Public Shared Function DivideByLengthPoints(ByVal doc As Rhino.RhinoDoc) As Rhino.Commands.Result
	Const filter As ObjectType = Rhino.DocObjects.ObjectType.Curve
	Dim objref As Rhino.DocObjects.ObjRef = Nothing
	Dim rc As Rhino.Commands.Result = Rhino.Input.RhinoGet.GetOneObject("Select curve to divide", False, filter, objref)
	If rc IsNot Rhino.Commands.Result.Success OrElse objref Is Nothing Then
	  Return rc
	End If

	Dim crv As Rhino.Geometry.Curve = objref.Curve()
	If crv Is Nothing OrElse crv.IsShort(Rhino.RhinoMath.ZeroTolerance) Then
	  Return Rhino.Commands.Result.Failure
	End If

	Dim crv_length As Double = crv.GetLength()
	Dim s As String = String.Format("Curve length is {0:f3}. Segment length", crv_length)

	Dim seg_length As Double = crv_length / 2.0
	rc = Rhino.Input.RhinoGet.GetNumber(s, False, seg_length, 0, crv_length)
	If rc IsNot Rhino.Commands.Result.Success Then
	  Return rc
	End If

	Dim points() As Rhino.Geometry.Point3d = Nothing
	crv.DivideByLength(seg_length, True, points)
	If points Is Nothing Then
	  Return Rhino.Commands.Result.Failure
	End If

	For Each point As Rhino.Geometry.Point3d In points
	  doc.Objects.AddPoint(point)
	Next point

	doc.Views.Redraw()
	Return Rhino.Commands.Result.Success
  End Function
End Class

import Rhino
import scriptcontext

def DivideByLengthPoints():
    filter = Rhino.DocObjects.ObjectType.Curve
    rc, objref = Rhino.Input.RhinoGet.GetOneObject("Select curve to divide", False, filter)
    if not objref or rc!=Rhino.Commands.Result.Success: return rc

    crv = objref.Curve()
    if not crv or crv.IsShort(Rhino.RhinoMath.ZeroTolerance):
        return Rhino.Commands.Result.Failure

    crv_length = crv.GetLength()
    s = "Curve length is {0:.3f}. Segment length".format(crv_length)
    seg_length = crv_length / 2.0
    rc, length = Rhino.Input.RhinoGet.GetNumber(s, False, seg_length, 0, crv_length)
    if rc!=Rhino.Commands.Result.Success: return rc
    t_vals = crv.DivideByLength(length, True)
    if not t_vals:
        return Rhino.Commands.Result.Failure

    [scriptcontext.doc.Objects.AddPoint(crv.PointAt(t)) for t in t_vals]
    scriptcontext.doc.Views.Redraw()
    return Rhino.Commands.Result.Success

if __name__=="__main__":
    DivideByLengthPoints()