Authors own the copyright to FOSS code they write. If they are contributing to a project, they (usually) allow the project to use the code using the same licens

Authors own the copyright to FOSS code they write. If they are contributing to a project, they (usually) allow the project to use the code using the same license as the project. In certain cases contributors may sign copyright assignment agreements, but the copyright doesn't go away. If the authors didn't retain copyright ownership, how would they enforce the terms of the license? The GPL would be unenforceable.