The most important change was to exclude the DsgnIntf.pas in the runtime package, because DsgnIntf.dcu isn't shipped with Delphi any longer. To create a application with your components and without using packages you need to exclude DsgnIntf.pas in your project. On the other side you need the file to register property editors and so on.

A resolution, and the cleanest one, is to make a runtime only package, that includes all the components and what ever you need during runtime. Everything you need to use only during designtime needs to be in a designtime only package.

In the case of the coolform components I created two new files. CoolFormDT.pas and CoolFormRT.pas. Both files have only the Register procedure for the appropriate package.

The Cool.dpk file is split into the CoolRTPackage.dpk and the CoolDTPackage.dpk. 

The CoolRTPackage.dpk contains the 
CoolButton.pas
CoolForm.pas
CoolFormRT.pas
ExtMaskGenerator.pas
maskgenerator.pas
maskgenerator.dfm
TRMemo.pas

This Package requires vcl50.dcp and is a runtime only package. So you can't install it in the IDE

The CoolDTPackage.dpk contains the
CoolFormDT.pas
MaskEditor.pas

This package requires vcl50.dcp and also CoolRTPackage.dcp and is a designtime only package. You need it to install the Components in the IDE and to register the MaskEditor.

What are in the different files and what changed?
CoolButton.pas

  contains the code for the TCoolButton component.
  deleted the Register procedure, moved to CoolFormDT.pas
  moved a little bit the lines, deleted blanks

CoolForm.pas

  contains the code for the TCoolForm component
  deleted dsgnintf in uses paragraph
  changed visibility of procedure MouseDown(...) and procedure DefineProperties(...)
  deleted the Register procedure, moved to CoolFormDT.pas
  moved a little bit the lines, deleted blanks

CoolFormRT.pas

  actual has no function. If CoolRTPackage should be a DesignTime and RunTime package
  you need to activate the Register procedure. But that's only for a resolution that's
  not so good. Best way is to delete this file.

ExtMaskGenerator.pas

  contains code to create the mask
  moved a little bit the lines, deleted blanks
  
maskgenerator.pas
maskgenerator.dfm

  contains UI and code for MaskGenerator
  moved a little bit the lines, deleted blanks

CoolFormDT.pas

  contains the Register procedure of the designtime only package CoolDTPackage.dpk
  registers the Cool components and the MaskEditor.

MaskEditor.pas

  contains code to make the MaskGenerator the Editor for the Mask property in the Object Inspector



I also included a CoolFormCollection.pce file to create a Delphi Package Colection (.dpc) file for easy install of new packages. I was afraid to add the .dpc file because it's size is about 2.3 MB and includes also the vcl50.bpl and vcl50.dcp.

I didn't check if this works with D3. (Sorry, was too lazy to install this product) But you can make it working with D4. You just have to change the required package from vcl50 to vcl40. Probably it is the same with D3 or something equal.