Now we have launched version 0.9.3 that uses a pure Java runtime instead of a hybrid one.
While the hybrid version of the runtime offers optimal system integration (for OS dependent functions like chown, chmod), it may have deployment restrictions on budget-friendly environments like shared hosting. The implementation of the hybrid runtime makes use of the PHP interpreter for some of the runtime function calls. However, in a shared hosting environment, operations such as process creation and sockets based communication are severely restricted or forbidden.
So we have decided to use Quercus for the few runtime functions that previously had an implementation requiring the presence of the PHP interpreter. Quercus is the Java rewrite of the PHP interpreter and exposes the Java implementations of the (de facto) standard PHP functions.
The question might arise why one might use nBB2 instead of phpBB 2. Since their functionality is identical, it's all about PHP vs. Java. Those who prefer the Java version of the lightweight phpBB 2 forum engine should go with nBB2. If you're wondering how easy is to deploy nBB2 in a shared hosting environment, stay tuned for a follow-up article on this topic.
For details, visit the project page at http://nbb2.sourceforge.net/.