The familiar and widely popular prepaid subscription model of cell phones inspired Microsoft to offer prepaid subscription of MS Office 2007. Users of South Africa and Romania can purchase license of MS Office 2007 for 3 months by paying approximately 30$ and can renew the subscription whenever they want.
With this business model Microsoft is primarily targeting students, small home businesses and home users who can not afford to buy the software in a single go payment. According to Microsoft Prepaid Edition official site
Microsoft Office Prepaid gives you the full power of the 2007 Microsoft Office system, with the flexibility to pay as you go and renew when you choose.
Microsoft is trying to push people away from free open source operating systems and office suits by making their products more affordable. At present this prepaid model is available only in South Africa and Romania and soon expanded to rest of the countries.