For what it's worth, the source code of OmegaSoft Pascal, a Pascal cross-compiler with linker/assembler/... for OS9/68000 targeting the 6809, is available: http://pascal-central.com/omega.html

Direct link to the archive: http://www.certsoft.com/PXK9_OS9_Source.zip

This seems to have been written in Pascal (Modula?).