Petite Chez Scheme is a complete Scheme system that is fully compatible
with Chez Scheme but uses high-speed threaded interpreter technology in
place of Chez Scheme's incremental native-code compiler. Programs written
for Chez Scheme run unchanged in Petite Chez Scheme, as long as they do
not depend specifically on the compiler. In fact, Petite Chez Scheme is
built from the same sources as Chez Scheme, with all but the compiler
sources included.

Petite Chez Scheme was conceived as a freely distributable run-time
environment for compiled Chez Scheme applications. To serve this purpose,
it needed to have a complete run-time environment, including, for many
applications, a working evaluator. The result is a system that is useful
not only to our customers for the applications they distribute, but also
to people who want to use a top-quality Scheme system and can't justify
purchasing Chez Scheme.

WWW: http://www.scheme.com/petitechezscheme.html