I’ve was wondering for quite sometime what is Office Live. Finally, after Microsoft lifted the NDA from Office Live, Jow Wilcox from Microsoft Watch explains:

Most of the Office Live capabilities derive from Microsoft server software, such as Exchange, SharePoint and Project. The service provides basic e-mail and calendaring capabilities (such as might be seen from Exchange), collaboration functions (such as come with SharePoint Portal Server) and for working on projects (such as supported by Project Server).

Something like Windows Live Custom Domains probably?

From Microsoft Watch