KeyKOS and Plan9/Inferno?
No. Their paths never crossed.
Which brings new OCapsOS Fuschia. We can't really explore the underlying Fuschia as it is R&D. We can look at the higher level app development in Flutter, how to embed it and explore its benefits with respect to KeyKOS. More so to celebrate the cap-lore 
work of Norm Hardy. Who Mark S Miller credits with his apprenticeship in computer security and life work toward solving computer insecurity.
On Saturday Nov 17, I attended a Flutter Study Jam taught by Emily Fortuna, a developer advocate on the Flutter team at Google. Here we developed our first Flutter App. The codelab is deliberately familiar to Android and iOS mobile app developers. Who typically used Android Studio, though tellingly Emily often referenced VS Code a more cross-platform IDE. page
Flutter is built on Dartlang and Dart on C/C++ kernel. Darts 2.0 Type System implements a strong mode alike JavaScript strict mode (ES6).
sound-dart
My hunch is though KeyKOS and Plan9/Inferno never crossed paths. Fuschia and Flutter already cross paths to provide a developer agnostic capabilities-based permissioning to make Safe Widgets.
We explore more and invite others to look at the possibilities. Apparently they are already. flutter-engine