As SugarCRM has no plans to distribute its next open source version (number 7) before 2014, SalesAgility, an important contributor to the community, has created a free and open source fork called SuiteCRM, which has just been released and aims to replace the Professional Edition of the customer relationship management tool.
SuiteCRM natively includes version 6.5.x of the Community Edition of SugarCRM and modules released and paid for under the commercial license for the Professional Edition (80% of the functionalities of these modules are available under the Community Edition).