I'd like to extend the WTP(e.g. custom personal wizard), I need to view the source code for WTP, then I can extend it.
BTW, I want to create my own "WTP", not just creating a personal wizard. Do you know where is the source code? So I can attach it to Eclipse and investigate it
Where can I get the source code for WTP?
You don't need to see the source of WTP to create a personal wizard. There is enough documentation (like here, an Eclipse article!). To be more specific for your problem, here is the link to create your own personal wizards!