Hi, the author of BuckleScript here. JSOO and BuckleScript has very different goals, the former focuses on the compatibility with native, while the latter focuses on the interop and optimal perf on JS backend. The progress of BuckleScript is actually much faster this year if you follow the development closely. OCaml as a language which has been developed for more than 20 years is quite usable without using the latest version, our top priority is to make js interop the best, it is not to catch up the lastest release (but we do have plans to sync up once every two years).