“I am still hoping to work on future enhancements of Orbiter, but I can’t make any promises or commitments.”
Orbiter has taught a generation of space nerds real orbital mechanics for free since the early 2000s. Its creator couldn’t keep developing it, so he published the source instead of letting it rot. It still depends on DirectX 7. That’s the honest way to retire a project, and more abandoned software should go out like this.