While Skype’s Windows and Mac desktop apps are well-known, the VoIP service also exists on Linux. And today, Skype is rolling out version 4.1 for the free, open-sourced operating system.

The new launch enables Skype users to sign in with their Microsoft account, after which your existing contacts from Messenger, Xbox, Hotmail and Outlook.com will magically appear in your Skype contacts.

This new version of Skype also means Linux users can now instant message with their Messenger friends straight from Skype, which is the first native support for this feature. That said, I’m not sure how many Linux users will be active on Instant Messenger, or have a Microsoft account, for that matter.

Earlier this month, we confirmed that Microsoft is set to retire its Messenger IM service in early 2013,  porting 100 million-plus users to Skype in the process, and this move today is part of that process. If you already have a Skype username, you will eventually have to merge the two.

In addition to this, the UI has also received a bit of a makeover, with Hotkey ‘d’ now invoking a dialpad during Skype-to-Skype and conference calls, and ESC letting you exit full-screen call view.

Interestingly, support for secondary log-ins has also been enabled with this launch, meaning you can run an additional Skype account simultaneously, and it has deployed support for the /golive command to make it easier to host conference calls.

Finally, Linux now supports Skype URIs, meaning Web developers can build Skype into their sites to initiate chats and calls directly from their pages.

Skype 4.1 for Linux is available to download now.

Skype 4.1 | Linux