Sankuru's free GPL downloads
Compiler construction
Simple, pluggable compiler and virtual machine in Php with support for casting plugin
Simple, pluggable compiler and virtual machine in Php with SWITCH/CASE statement plugin
Pluggable compiler and virtual machine in Php with BREAK and CONTINUE statements plugins
Pluggable compiler and virtual machine in Php with FOR statement plugin
Simple compiler and virtual machine with plugin architecture. Make your own cc and vm plugins!
Simple Turing-complete compiler (TL) and virtual machine with support for the IF, WHILE, and DO WHILE statements
Bytecode compiler and virtual machine in Php for a simple expression language
Using Bison parser tables in Php
SimpleLang - Using PCRE as a lexer in Php
Dijkstra's shunting yard algorithm in Php
Map/Reduce-style programming in Bash