GNU Kawa (Scheme on Java) had its first public release I can find in 1998, with version 1.6. It compiles to Java bytecode since version 0.2, and is now at 2.0,

GNU Kawa (Scheme on Java) had its first public release I can find in 1998, with version 1.6. It compiles to Java bytecode since version 0.2, and is now at 2.0, and still actively maintained by the same single developer as far as I can tell. It's pretty impressive, despite not being widely known.