You might have missed the news just before the holidays that Microsoft has become slightly more open with respect to its networking protocols. Late last year, they announced a way for third parties to license their core file sharing protocols through an independent organization called the Protocol Freedom Information Foundation.
This is good news on several fronts.
First, it means that your Linux and Mac clients wont be left out in the cold when Microsoft upgrades its Windows Server 2008 software later this year, and be able to fully continue to participate on Microsoft networks and share files and print servers with Windows users.
Both of these OSes make use of Samba, which will be the first licensee to take advantage of this arrangement. In the past, Samba had to resort to some clever programming tricks to stay on top of changes to these protocols.