In case anyone except me still uses this, I've fixed the videos to work with the new API. Bombcasts probably work but are untested. Source is available at https://github.com/jncr/GB-android and you can get the apk from github at https://github.com/jncr/GB-android/raw/master/giantbomb.apk . You'll probably need to uninstall the old version before installing this one, and it only streams in HQ.
I'm a PHP developer so probably won't be doing any ongoing work on this, but if it breaks again I'll probably fix it again.