This is Moscow ML, a lightweight implementation of Standard ML:

The current version of Moscow ML
  * implements the full Standard ML language, as revised 1997,
    including Modules and some extensions
  * yet is backwards compatible with versions prior to 2.00
  * implements large parts of the new SML Basis Library
  * implements separate compilation
  * can produce compact stand-alone executables (a la Caml Light)
  * supports quotations and antiquotations, useful for metaprogramming
  * supports dynamic linking of external functions