The study deals with the features open source CRMs have, the ways we can change the code and make our own open source CRM system. The research is oriented to Web based CRMs. One open source CRM system is modyfied and translated into the Lithuanian language. Installation files were created for people who do not know databases and Web services software in order to help them install this CRM system and configure database as well as other system requirements. The final result of our work is open source CRM system called „OfisasTinkle2006“. This product is used by a couple of firms in their business sphere.