Alfresco, whose open source enterprise content management (ECM) software has earned it a significant following, is making more waves with the release this week of Alfresco Labs 3, an open source alternative to Microsoft SharePoint.John Newton, the CTO of Alfresco Software, gives a good summary of why they're targeting SharePoint on his blog:

The main feature delivered by Alfresco Labs 3 is that Microsoft Office can seamlessly access the repository in the same way that it works with Microsoft SharePoint Server. This could mean significant savings for many enterprises.

Other features in Alfresco Labs 3 include Surf, their Web application development platform; Alfresco Share, a new social computing application developed using Surf; and a document library capable of scaling to more than 100 million documents. That's impressive functionality, and the fact that it's open source sweetens the pot.

Interestingly, the SharePoint protocol that makes the Alfresco Labs 3 possible was released as part of Microsoft's compliance with the European Commission's orders in 2004. To the best of my knowledge, no other vendor -- open sources or otherwise -- has released a SharePoint-compatible repository server.

For additional information on Alfresco Labs 3, including details on downloading and installing it, check out the Alfresco Labs 3 entry on the AlfrescoWiki. Alfresco has long been a good resource for solid open source ECM, and this added functionality serves to make it even more compelling.