libposix is an impementation of the core functionality of all Unix systems. It is a full, cross-platform implementation of the POSIX 2008 standard. It is meant to replace existing implementations of a Unix system's core libraries. It is an exact implementation of POSIX 2008 and nothing else (no extensions, no previous POSIX versions). However, it works well with possible extensions to the core system functionallity (for example, GNU or BSD).
Components 4 Java is a development tool for Java. It provides a framework to organize and separate different parts of code, and fills the gap between the class level and the library level as provided by the Java SE architecture. Additionally, you can organize your classes in well-separated and loosely coupled components. Those can be stuck together graphically into larger compositions. Finally, components and compositions will be distributed among Java archives as specified in assemblies.