OpenSMTPD is an RFC compliant, secure, and simple SMTP server ported from OpenBSD to Linux. It supports the SMTP protocol, including SSL versions for added security, virtual domains, forward files, and external delivery agents like procmail, and can do most of the basic things that other MTA implementations do.
HGL is a compiler/interpreter suite for developing images. It features its own simple but powerful language, Lua integration, output in various formats as well as runtime input handled by plugins, and easy integration into various environments like Web servers or graphical applications. The input is taken from a source file, which has to be compiled for quick and frequent access by the interpreter. An interpreter then runs the compiled files, takes input from custom plugins (if neccessary), and outputs its result via custom plugins.
YYAST is a library which completes Lex and Yacc by adding an Abstract Syntax Tree (AST). It is designed so that you write as little as code as possible in the Lex and Yacc grammar files, so that it doesn't distract from the grammar of the language, and is intended to make it easier to use high level programming languages for compilers.