This feels a lot like what happened to Hack, which at first was compatible with PHP and could be compiled to it, but later became its own language to better fit FB's needs, and it seems like they're giving OCaml the same treatment here with ReScript.
There was actually some effort being made to keep OCaml tooling compatible with ReasonML (which is supported by dune[0] with no additional configuration) and BuckleScript integration with dune, which was being worked on before this rebrand, so it's kind of sad to see FB going off on their own with ReScript because they don't wanna do the work to upstream the changes they need.
By the way, regular OCaml also has its own JS backend[1] which is of course completely incompatible with BuckleScript.
There was actually some effort being made to keep OCaml tooling compatible with ReasonML (which is supported by dune[0] with no additional configuration) and BuckleScript integration with dune, which was being worked on before this rebrand, so it's kind of sad to see FB going off on their own with ReScript because they don't wanna do the work to upstream the changes they need.
By the way, regular OCaml also has its own JS backend[1] which is of course completely incompatible with BuckleScript.
0: https://dune.build/ 1: https://github.com/ocsigen/js_of_ocaml