It's not yet Beta 3, but the newest test build of Windows Server Longhorn was released to a select group on February 16.
Microsoft made the private February Community Technology Preview (CTP) build of Longhorn Server available for download via Microsoft Connect. The newest build is Number 6001.16461.070209-1510.
The February CTP will be the first Windows Server release to have the firewall on by default, according to testers. When upgrading, if a machine's firewall was initially turned off, it will remain off after the upgrade. But the main Longhorn Server roles (Active Directory Domain Controller, DHCP Server, DNS Server, IIS Web Server, Terminal Services, Distributed File System, File and Printer Sharing and Identity Management Server for Unix) will work out of the box with the Longhorn Server firewall on by default, according to the Softies.
Longhorn Server is designed to be componentizable and modular. Microsoft partners and customers will be able to choose among 20 different roles when configuring the product. Longhorn Server also will add a number of new, previously disclosed features, including Internet Information Services 7.0; Network Protection and Access capabilities; and terminal services gateway support.
Microsoft did not release a January CTP test build of Longhorn Server, as the company originally expected to do. (That might be because the slated November CTP slipped into December 2006.) Officials said last fall that they were planning to release Beta 3 of Longhorn Server in the early part of 2007, some time after releasing the January (now February) CTP.
The final Longhorn Server release is due out in before the end of calendar 2007.
Update: ActiveWin.com posted the text of the Longhorn Server February CTP notification Microsoft sent to testers.