The [link|http://www.openoffice.org/licenses/sissl_license.html|Sun Industry Standards Source License] and the LGPL seem to be the relevant licenses here... I also checked the help(?!) and found this:
XML file format names
If in the dialogs for saving and opening OpenOffice.org documents you do not select any other file type, OpenOffice.org uses the following XML formats:
Application
File extension
OpenOffice.org Writer
*. sxw
OpenOffice.org Writer templates
*.stw
OpenOffice.org Calc
*.sxc
OpenOffice.org Calc templates
*.stc
OpenOffice.org Impress
*.sxi
OpenOffice.org Impress templates
*.sti
OpenOffice.org Draw
*.sxd
OpenOffice.org Draw templates
*.std
OpenOffice.org Math
*.sxm
Master documents
*.sxg
These file name extensions on the one hand allow better differentiation if you are searching though a lot of files of different file types in a directory. And on the other, from the name, it is clear that compressed XML files are involved that must first be unpacked before being read, for example, by a text editor.
If you want to work permanently with another file format, you can define that format as the default. Choose Tools - Options - Load/Save - General to find alternative file formats that can be selected for each OpenOffice.org document type.
XML file structure
The OpenOffice.org XML file formats are compressed according to the ZIP method. Use an unpacking program of your choice to unpack the content of an XML file with your subdirectories. You see a structure similar to the following illustration.
<snip>... ...</snip>
The text content of the document is located in content.xml. You can view this file with, for example, a pure text editor.
By default content.xml without indents is stored at the start of the line in order to minimize the time for saving and opening. By choosing Tools - Options - Load/Save - General you can change this procedure so that the lines are saved with a structured indent.
meta.xml contains, inter alia, the meta information on the document, which you can enter underFile - Properties.
If you save a document with security, only meta.xml is not secured.
settings.xml contains further information on settings for this document, for example on the printer, on the recording of changes, the associated data sources and so on.
In styles.xml you find the Styles defined for the document that can, for example, be seen in the Stylist.
The meta-inf/manifest.xml file describes the structure of the XML file.
Additional files can be contained in the packed file format. Illustrations are, for example, contained in a Pictures subdirectory, Basic code in a Basic subdirectory and linked Basic libraries are found in further subdirectories of Basic.
Definition of the XML formats
The DTD (Document Type Description) files can be found in {installpath}\\share\\dtd.
Note that the formats are subject to certain licenses. You can find notes on the licenses at the start of the DTD files. More detailed information can be found on the OpenOffice.org website.