In that particular example, the only misleading things are the indentation, and the lack of block delimiting for the inner match. The language grammar is accepted by the grammar compiler bundled with OCaml, which doesn't like ambiguous grammars.
> - f*-up licence (open-source, but modifications can only be distributed as source-code patches)
I didn't look at the license very closely, but there are a few forks of the language out there (check out github), which aren't distributed as patches.