Will Ubuntu have something like Google App Inventor to easily develop applications for the Ubuntu platform? Is Quickly intended to do that? I heard Ubuntu is planing to make easy and fun to develop for Ubuntu platform. How is it going to be accomplished?
This is a proprietary commercial application that costs $39.85 US (available from Ubuntu Software Centre) and seems to be offering what you are looking for. As far as I can tell, it is a GUI where you set out a flow chart of user interactions.
I would recommend you try quickly. It allows you to easily create applications. It generates a project template containing much of the required boilerplate code that you can then edit. It allows you to design the user interface in Glade, a graphical designer.
Quickly also handles packaging and uploading to PPAs.
Developing for Ubuntu comprises a number of sections which it's important to think about as separate but associated elements:
When starting off a brand new project there will always be a set of best practices to follow and easiest routes to take. These are codified in the quickly project which provides a set of instant use templates for various languages and coding problems. Right now I believe templates exist for python, vala and pygame.
Ubuntu platform uses the launchpad service in order to provide a place online where code can be shared, bugs can be tracked and other project management tasks can easily be performed. This service is where translations are done, teams are set up and even support questions are asked.
You can integrate project management into your desktop work flow using a range of tools. From the fancy GUI GroundControl to command line tools for tracking bugs and running reports.
The source contents of a project in Ubuntu are normally stored in a bazaar branch. These branches are generally files with your project in launchpad, but they don't have to be. There are some pretty extensive tools on the Ubuntu platform for dealing with code branches, everything from the bzr command itself to bzr-gtk and the aforementioned GroundControl.
This is the last step in the process and it allows you to get your app to more users, for testing and for true distribution. First it's a matter of creating viable deb packages, there are various guides on how to make Debian packages; but the aforementioned quickly creates the standard templates for you to work from.
The launchpad ppa system was developed to allow quick distribution channels without too much checking or verification. Your Debian packages can be submitted to launchpad under any person or group that you have ownership or membership in.
However the best route to take is to take your packages to the Debian project where they will be submitted for review and if they pass can be uploaded directly into the Debian repository and available in the next version of Ubuntu. There are a host of tools for helping with this process, but it's not yet as easy as the other steps mentioned above.
Ubuntu probably won't include App Inventor by default, but is far as i can see on the setup page, Ubuntu is supported, and it even has a deb package.
As far as the Ubuntu strategy for development, I'm not too sure. My guess is Python. You should submit this as a separate question.