Now that the doors of Google App Inventor are officially closed, MIT has taken the reins and has recently made the code for the project open source for the community and world to tinker with. The news pretty much stops there for now though. There is very little in the way of documentation and support for the service currently. They haven;t set up their servers yet, so you have no where officially to upload your modifications. It is still a big process and large undertaking. MIT wants to get everything set up and working flawlessly before they open up the servers to the public. We can respect that.
The most recent update from MIT slates the service to be up and running in Q1. They have a beta service available for you to get in, but you need to fill out the request form and they will grant you access as soon as they can. Much like when App Inventor first launched.
If you are eager to keep up to date with App Inventor and its new home at MIT, be sure to keep an eye on their news at  appinventoredu.mit.edu.
Source: MIT via Androidpolice