I cloned Objective Resource from the yfactorial ObjectiveResource github repository, initialized the git submodules, and tried building it under the SDK for 4.2.
I ran into two problems when trying to build. First, it complained about not knowing where the SDK was. To remedy this, I went to Project -> Edit Project Settings -> Build -> Base SDK, and changed it to latest. It was originally looking for the 3.0 SDK, which wasn't installed on my machine.
Next, it complained with the following errors:
: error: CFBundleIdentifier 'com.yourcompany.objective_resource' contains illegal character '_'
: invalid bundle identifier 'com.yourcompany.objective_resource'
I fixed this by following the instructions for ['com.yourcompany.App_Name' contains illegal character '_'](http://www.iphonedevsdk.com/forum/iphone-sdk-development/17865-strange-error-after-updating-3-0-sdk.html). Basically go to Project -> Edit Active Target -> Properties and change identifier from ...identifier} to ...rfc1034identifier}
Hope this helps someone out!