BESEN is an acronym for "Bero's EcmaScript Engine", and it is a complete ECMAScript Fifth Edition Implemention in Object Pascal, which is compilable with Delphi >=7 and FreePascal >= 2.5.1 (2.4.0 only inoffically).
Moved to Google Code http://code.google.com/p/besen/
BESEN is really the _first_ ES5 complete engine. It helped me many times to analyze the ECMA-262-5 spec when all major browsers didn't implemented even partly ES5. I also used Rhino to test ES5 at that time. But in contrast with BESEN, Rhino didn't implement the strict mode. Dmitry.