inherit from a base form , and the base form come from a lib

Hi all ,

I have a question about inherit a form from a base form that come from
library .
First I create a library for my all base forms , named "GBaseForm.pbl" and
create some base forms , then add all the base form to "Object Repository" ,
all these are successful . finally build the package to "GBaseForm.lib" .
Then , I create a new application , add the "GBaseForm.bpi" as one of
runtime package (vcl is also in the runtime list ) . so I create a new form
inherited from the base form through "New Items" popup window , a new form
has created , but the base form was also be add to the new application , how
this happened? When we inherit from TForm , no file is add to my application
, how does vcl do it ?

Need your help , any mentioned ? Thanks .