joomla/joomla-platform — pull request #686 by romacron (2011-12-31 12:24:46+00:00)
Title: new self, you are able to extends the jform with the extended instance 

JForm::getInstance(**); works fine.

for extra formhandling like

class myForm extends JForm{
}

$personalForm=myForm::getInstance(**);
it gets the instance of JForm
i am not able to get the instance of myForm