You can manage which projects are active and retired from the GTD settings page.
Context:
The license for your organization determines the maximum number of projects that can be
active simultaneously. If your group has created the maximum number of projects, you must
retire an existing project before creating a new project.
From the home page,
click Administration.
Locate the project you want to disable.
Click Retire.
Note:
You can click Activate to enable a previously
retired project.