B4j compiles to java, which Evans it is cross platform.
You can create complete webservers and webapp ( not just scripts, but complete solutions ), create Windows apps and OSX apps. You can even run them (webservers or webapps) from any browser enabled device!
1. Desktop applications.
2. Backend solutions using jServer.
3. Web apps with ABMaterial or with jServer WebSockets directly or with a simpler solution such as Skeleton: https://www.b4x.com/android/forum/threads/skeleton-css-library.82128/#content
4. IoT applications that run on Linux boards such as Raspberry Pi.
5. Console applications.