Basically this project expect following deliverables.
1.) Nuvem message queue API ( This should be a Nuvem specific and vendor independent API)
2.) Implementations of above API for major cloud vendors such as GAE, Amazon etc.
3.) Standalone implementation of above API. You can use one of message queue framework such as ActiveMQ, QPID etc.
I highly recommend you to go trough existing components to understand above deliverables properly. key-value data service component can be a good example to follow.
It's look like you have confused with GAE Task queues with message queues ( i.e - GAE Task queue is a way of scheduling your back ground jobs and nothing to do with messaging). For Amazon cloud you can use SQS but for GAE there is no in-built messaging service instead you need to integrate a 3rd party queue framework which based on GAE menarche, refer following post to find out more details.
 - http://activemq.apache.org/
 - http://qpid.apache.org/
 - http://aws.amazon.com/sqs/
 - http://stackoverflow.com/questions/625146/memcache-based-message-queue-for-app-engine