Every edition of 1CRM comes with the source code of the CRM system. This provides you with insight into the functionality of 1CRM and the opportunity to modify it to suit your needs. 1CRM can also be used as a platform to create CRM extensions. You can sell them, or provide them as open source software to the community.
1CRM is not a pure open source solution, as you will not be allowed to modify the source code of 1CRM and then sell it without license. 1CRM is often called an open source CRM system with the addition of commercial open source, because it excludes the files on which the license and user management of the CRM system is implemented.