Innersource

Using open source approaches and processes, but for proprietary software.

From GitLab: Organizations that use InnerSource experience benefits that are typical of open source development, such as:

High-quality code: With unit tests, code coverage, and continuous integration, teams improve code earlier in the lifecycle
Comprehensive documentation: Code is better documented, both in comments and less formally in discussions, leading to a single source of truth
Effective code reuse: Code and architecture are discoverable and available across teams and the organization
Strong collaboration: Code reviews have less friction, team communication becomes stronger, and contributions increase in number
Healthy culture: Silos are broken down, so developer happiness improves, leading to better retainment and recruitment