The version 0.9 is out. While the last version post here was 0.3, but that doesn't mean that the project was dead. In fact, I am using this in most of my (JVM) projects now - and I am not willing to go back to other build systems.
Anyway, what has changed since 0.3? Mostly quality of life things. For example, converting existing IntelliJ project into Wemi can be done with a single button click (at least for simple projects, complex ones may need some tweaking), Maven dependency resolution has been vastly improved (mostly for correctness), CLI gives some nice real-time feedback on running tasks, and, of course, many bug fixes and improvements.