As the publisher description states this is an extended version of open office and it is fully compatible with the popular Microsoft Office 2007 suite , but you don't have to pay for it.
Yes it is completely free and you can install it on as many computers you want and use it as long as you want. It includes substitues for word, excell , powerpoint , access , but not outlook.
The full package includes : Writer - Word , Calc - Excel , Impress - Powerpoint , Base - Access , Math , Draw
Most of the tools and the butons look very similiar to Macrosoft Office tools so people used to their products will not feel lost.
Oxygen office is the extended version or Open Office and it is fully compatible with Microsoft Office 2007 and previous versions, so it shouldn't be confused with Open Office which is only compatible with office 2003 and previous versions.
In the tools Menu you can change the default Save formats to Microsoft Office and any document you create can be send via email to people that only have Microsoft Office.
It doesn't have some advanced featues of the Microsoft Word and Excell , like advanced mail merge options and filter options , but for most people it save them buy the expencive Microsoft Office Package.