Today every organization relies on software systems to provide it with an effective and efficient way to deliver products and services. However, it is a challenge for companies to keep up with existing knowledge and to adapt to new software developing capabilities. While advances in technology have made it possible to efficiently access and use existing knowledge, even if it is distributed across the globe, technology is also becoming increasingly complex, and software systems are now expected to provide advance capabilities that support the ubiquitous interactions of users and complex processes of companies. Therefore, when developing software systems, it can be advantageous to implement some functionalities by using existing knowledge, thus adopting a "not-reinventing the wheel" strategy. For an organization, choosing which components to buy or to contract externally is a make-or-buy decision. The evaluation of make-or-buy decisions is a crucial topic for every [...] book focuses on such make-or-buy decisions in software development. To provide a holistic view of this decision making in an organization, we look at the factors influencing it at a strategic level implemented by management, on the project level and by the decisions made by the software developers themselves. Focusing on the state of the art, we assume bounded rationality and look at the cognitive biases that influence these decisions. In doing so, we aim at providing a better understanding of decision making in general and the use of external software artifacts during software development in particular.