Open-source software (OSS) is used today by almost all private users, companies, and public organizations. Since it has an open source code, any user can tailor or adapt OSS to their own needs under given licensing conditions. However, customization of OSS occurs only rarely. Steffen Kessler identifies various reasons for this and develops a process model for the adaptation of OSS in user companies. Based on this, he derives specific requirements for configuration and change management and structures the possible state transitions of the software source code. He then examines the extent to which common control models for managing software development and deployment, such as COBIT or the ISO/IEC 15504 standard, can support the adaptation of OSS. His process model can enhance the management of OSS.