1) it uses templating (in our case, HTML, Android XML, and XIB) 2) it is cross platform, runs everywhere, even server 3) it produces native apps
It's different in this sense:
1) it doesn't do DOM diffing, it does two-way data-binding 2) it's statically compiled to native code, it doesn't try to run JS in native platforms, and doesn't require any async seems between between the native platform (it's all static linkage)
There may be other differences. The audience is Java and people who want no-compromise native integration. We target 70% code sharing between platforms, but expect the UI to be rebuilt for each platform.
The core engineers behind J2ObjC were those who built Swing at Sun. We're pretty sour on the idea that write-once run-anywhere UIs are possible. Best experience dictates custom design for each frontend IMHO, and shared UI widgets may get you into an 'uncanny valley' state where you're composing the native widgets in ways that are alien to platform specific style guidelines.