A NSIS installer is never going to be a one page wizard because the actual installing happens on a 2nd page.
There are probably two ways to create the every detail on one page wizard:
Use Resource Hacker to edit the directory page in one of the NSIS ui's in NSIS\Contrib\UIs to add a richedit control and in the script use
ChangeUI
to apply this new page then at run-time use one of the license plugins to fill the richedit control.Create a custom page with nsDialogs.