Currently, you can define 10 user accounts in the Windows Home Server Console and you can install the Windows Home Server Connector software on up to 10 home computers running Windows XP or Windows Vista.
In all of the secondary research that we reviewed and primary research that we did for home server as part of the product planning process, it was very rare to find broadband connected households and home-based businesses with more than 10 people and with more than 10 home computers. Additionally, Microsoft offers a great product, Windows Small Business Server, that scales well beyond 10 users for more sophisticated home-based businesses or small businesses that plan on growing. You can read about the upcoming release of Windows Small Business Server 2008 on the microsoft web site.
We didn't want to build a consumer product that used CALs (Client Access Licenses) as we really didn't think consumers wanted to deal with managing licenses for their home PCs and sometimes when you say CAL, people hear "cow" and respond that they live in the city not on a ranch and don't really have a need for cattle.