I am not sure why you are having the early binding issue. If you build your driver from the driver templates they are already setup do to the early and late binding properly so this shouldn't be a problem. If you changed any of the original code that was created via the template try undoing those changes.

IFocuser is an interface that specifies the standard, mandatory methods and properties of every ASCOM focuser driver. Do a google search or msdn search for more info on .NET interfaces.

One guess as to the reason all of those drivers are failing Conform: Maybe they were written back before the release of ASCOM Platform 5.5. The current version of Conform checks that drivers conform with the current version of the Platform. There were some changes made to the way drivers are registered in the new platform update. It is up to the device manufacturers to make sure that their drivers are up to date and work properly with the most recent version of the Platform. Hence, there is a newer version of the OptecTCF driver that is available for download on their website that does pass conform!

If you are trying to update an older driver it might be helpful to build a new driver project from the current template and look at the driver.cs. Compare the way that the new one does the registration to the way yours does the registration and try to make them alike. The old drivers used a component called Helper or Helper2 to do registration and now it has been moved to a new component called Utilities. You will need to download the utilities class and add a reference to it in your project.

You should end up with something like this...

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Windows.Forms;

using ASCOM;
using ASCOM.Utilities;
using ASCOM.Interface;


namespace ASCOM.OptecTCF_S
{
//
// Your driver's ID is ASCOM.OptecTCF_S.Focuser
//
// The Guid attribute sets the CLSID for ASCOM.OptecTCF_S.Focuser
// The ClassInterface/None addribute prevents an empty interface called
// _Focuser from being created and used as the [default] interface
//
[Guid("4103b899-c887-4f8b-a085-8be9e1ebc183")]
[ClassInterface(ClassInterfaceType.None)]
public class Focuser : IFocuser
{
    //
    // Driver ID and descriptive string that shows in the Chooser
    //
    internal static string s_csDriverID = "ASCOM.OptecTCF_S.Focuser";
    private static string s_csDriverDescription = "Optec TCF-S Focuser";    //Displayed in Chooser

    //
    // Constructor - Must be public for COM registration!
    //
    public Focuser()
    {
        // TODO Implement your additional construction here
    }

    #region ASCOM Registration
    //
    // Register or unregister driver for ASCOM. This is harmless if already
    // registered or unregistered. 
    //
    private static void RegUnregASCOM(bool bRegister)
    {
        //Helper.Profile P = new Helper.Profile();
        Utilities.Profile P = new Utilities.Profile();
        P.DeviceType = "Focuser";                   
        if (bRegister)
            P.Register(s_csDriverID, s_csDriverDescription);
        else
            P.Unregister(s_csDriverID);
        try                                     
        {
            Marshal.ReleaseComObject(P);
        }
        catch (Exception) { }
        P = null;
    }

    [ComRegisterFunction]
    public static void RegisterASCOM(Type t)
    {
        RegUnregASCOM(true);
    }

    [ComUnregisterFunction]
    public static void UnregisterASCOM(Type t)
    {
        RegUnregASCOM(false);
    }
    #endregion