crypt_blowfish is an efficient implementation of a modern password hashing algorithm, based on the Blowfish block cipher, provided via the crypt(3) and a reentrant interface. It is compatible with bcrypt as used in OpenBSD. It is adaptable to future processor performance improvements, allowing you to arbitrarily increase the processing cost of checking a password while still maintaining compatibility with your older password hashes. The hashes it produces are several orders of magnitude stronger than traditional Unix DES-based or FreeBSD-style MD5-based hashes.
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).