In Project Server 2010, there is a "Notes" field at the level of the project (different than the one at the level of the task). This field can be added to the Project Details Page but remains disabled. Can anyone tell me please how this field gets populated or where it retrieves notes from? Our company wants to keep track of the weekly project notes so I am exploring if I can use this field for this purpose. Thank you.
All of the project level summary information like Start/Finish dates, total duration and so on is stored in a task with TASK_ID == 0.
Task Note or Project note in your case is stored in MSP_TASKS.TASK_RTF_NOTES column. Here is a good article how to read the field and use it in reports: http://blogs.msdn.com/b/chrisfie/archive/2008/06/04/how-to-display-microsoft-project-task-s-notes-field-in-a-report.aspx.