Original contribution is located here:
I don't suggest to use it on production sites because I see that 1.03 version is not final:
I had an autoinstaller for 1.02 and a new account was created when the password field was entered on the checkout.php page.
I have upgraded to 1.03 and see that the password filed is present but a new account is not created if you fill it.
I have changed only one line in the:
to fix the checking if the Gift Voucher Contribution is installed