Can I use ArcXML format in my own application?

Hi,

I'm working on GIS software for PDA.
I want to add open/save project feature and I'd like to use ArcXML format
(ArcPad project format is based on ArcXML too).
As I see, ArcXML reference includes only copyright 
information about the document itself, so that's not exactly what I need.

My question is:

Am I allowed to use ArcXML as a project format for my own application?
Users of my application will be able to do following operations:
- open/save project created by my application
- create and save project in my application and open it in ArcPad
- create and save project in ArcPad and open it in my application

Could anyone give me a piece of advice 
regarding to the copyright and terms of use of ArcXML?

Thanks in advance
Cheers

-- 
Mateusz Łoskot
http://mateusz.loskot.net