Problems using Maven to initialize a local thoughtsite (App Engine sample) project in Eclipse

Question

This sample app ("thoughtsite") for App Engine contains a pom.xml in its trunk:

http://code.google.com/p/thoughtsite/source/browse/#svn/trunk

I ran mvn eclipse:eclipse and also tried using m2eclipse to import this source code into an Eclipse project.

But I end up with this error despite the fact that I have the Google App Engine plugin and the Google App Engine SDK installed:

Exception in thread "main" java.lang.ExceptionInInitializerError
    at com.google.appengine.tools.info.SdkImplInfo.<clinit>(SdkImplInfo.java:19)
    at com.google.appengine.tools.util.Logging.initializeLogging(Logging.java:36)
    at com.google.appengine.tools.development.DevAppServerMain.main(DevAppServerMain.java:82)
Caused by: java.lang.RuntimeException: Unable to discover the Google App Engine SDK root. This code should be loaded from the SDK directory, but was instead loaded from file:~/.m2/repository/com/google/appengine/appengine-tools-sdk/1.3.0/appengine-tools-sdk-1.3.0.jar.  Specify -Dappengine.sdk.root to override the SDK location.
    at com.google.appengine.tools.info.SdkInfo.findSdkRoot(SdkInfo.java:106)
    at com.google.appengine.tools.info.SdkInfo.<clinit>(SdkInfo.java:24)
    ... 3 more

When I go into the project settings under "Google" and try to set it to use the default App Engine SDK it always reverts to trying to use Maven's App Engine SDK instead. No idea how to get this project working.