SugarCRM - Commercial Open Source

SugarCRM offers both enterprise and professional commercial editions of their open source product, "Sugar Open Source". These editions extend the base open source product with additional features plus software support.
SugarCRM believes their combination of open source development with commercial addons and support enable them to provide better value for their customers CRM dollars. Their products have been translated into 40 languages with the help of 4,500 community developers and over 150 business partners. The Sugar Open Source software package has been downloaded over 1,700,000 times.

Their CRM solution may also be paired with the seemingly endless commercial and open source addons available at SugarExchange and SugarForge, respectively. These additional products provide integration with other software such as Asterisk PBX's, LDAP authentication databases, etc.

You may also use their hosted edition, Sugar On Demand. Unlike other hosted solutions, you can transfer from their Sugar On Demand to a self-hosted setup at anytime. This can provide a lot of flexibility to businesses as they grow and their CRM needs expand.