The form is complete, but you are free to make further changes to the document. If you were sending this out to other people to complete, you would probably want to make the document read-only. The effect would be that users would be able to fill in the form, but not to make any other changes to the document.
To make the document read-only, select Tools > Options > OpenOffice.org > Security > Open this document in read-only mode.
If the document is read-only, anyone filling in the form will need to use File > Save as to save the document.