Legacy Systems are systems that you might be too afraid of to change. But they are necessary because they make all the money for your company. Thus, developers often have to maintain these older systems whether they want or not. Legacy systems have their own fascinations and challenges that can be much more interesting than just gluing together some frameworks in a green-field project. But the lack of knowledge about how to tackle legacy systems is a big problem. Most developers just learn how to create new systems initially and not how to maintain existing ones or even evolve those systems. This list tries to close these gaps.
Markus curates this list on GitHub, like other awesome-* lists do. He‘s happy to take pull requests!