Instead of forking JavaFlow let me invite you to try out my own fork 
There are a lot of original design issues fixed (like omission of continuable method “markers” that leads to aggressive stack capture before any method call), Java8 support is added (for ex., lambdas are supported). And as an icing on the cake there is an async/await implementation atop of this (GitHub - vsilaev/tascalate-async-await: Async / Await asynchronous programming model for Java version 1.8 though 17; similar to the functionality available in C# 5. The implementation is based on continuations for Java (see my other projects).) – currently implemented as Java Agent, but compile-time Maven plugin will be available shortly. I would really appreciate if you try it out and left a feedback – never tested my code with other JVM languages.
Plus, there is another rework of JavaFlow that looks very promising:
It’s almost a complete departure from JavaFlow from user API stand point, but the core idea is very similar.