The Cocotron is an open source project I released back in 2006 and ran for a number of years. It has it’s own website here: cocotron.org . There is some information about projects I know of which successfully used it here: https://www.cocotron.org/Examples
While Cocotron initially targeted Windows it largely lives on as a macOS compatibility layer for FreeBSD in ravynOS here https://airyx.org
I haven’t been actively working on Cocotron, larger shifts to iOS and Swift have made the project less relevant but it still exists and is free to use.
Cocotron use in iOS compatibility layers
Cocotron was also used by a few companies trying to capitalize on an iOS compatibility layer, two for Android and one for Windows.
I was contracted by Apportable to get some of their early demonstrations working for seed funding, I declined to join the company. They built their layer using a mix of Cocotron and other open source projects.
Apportable source information: https://github.com/apportable/Foundation
Apportable Crunchbase: https://www.crunchbase.com/organization/apportable
I don’t know the provenance of Microsoft’s WinObjC, it looks like they acquired it from somewhere else. The history is a little troubled in that they have been fairly deliberate in erasing the Cocotron history from the source. Anyway, here is a link to a discussion about their use of Cocotron and removal of licenses. Sadly they never made much of an effort reach out to me.
Microsoft’s WinObjC project: https://github.com/microsoft/WinObjC/issues/35
Stella was an effort to create another iOS compatibility layer around the same time as Apportable. I don’t know the final disposition but it looks like they had some level of success. I was contacted by the founder and asked to join the company but also declined this.