Miguel, ActiveWeb and all of JavaLite is compatible with Java 8. We have been running our commercial systems on Java 8 since March 2014, before Java 8 came out officially.
The only limitation is if you use ActiveJDBC with dynamic instrumentation and inside Lambda expression. It is documented here:
However, if you use static instrumentation with ActiveJDBC, then you have 100% compatibility with Java 8. Other than that, we have not experienced any issues since we started using Java 8.
Thanks
igor