1st of all if the developer says he won't use the 301 then he's one very strange developer it's the basic of frontend development. But that being as it is, 301 is the best and most viable option but you do have a few other:
- tell GWT your prefered domain.
- have the devloper make a dynamic rel canonical, something like this (in php)
' ?>
in the above situation he of cause would have to make a function called checkURL to test for if the url begins with http://www and returns the right formatted version. and tell GWT what domain you prefer.
But again the only right way is a 301 and it's ridiculously simple to make.

