You don't lose OTP, because OTP is a library, written almost entirely in Erlang (not counting the set of NIFs/BIFs which provide intrinsic functionality), which

You don't lose OTP, because OTP is a library, written almost entirely in Erlang (not counting the set of NIFs/BIFs which provide intrinsic functionality), which we absolutely aim to compile with Firefly just like any other Erlang (or other BEAM language) sources. The BEAM also provides a runtime, but that runtime can be implemented using other strategies. It essentially provides a M:N green threading abstraction (processes), with a specific set of semantics around how those communicate (messages) and how failure is handled (links/monitors/etc). Firefly provides a runtime that aims to be equivalent to that of the BEAM from the perspective of the developer, the only difference is in how that is done behind the scenes, what is produced by the compiler, and what restrictions we impose that the BEAM doesn't (namely no hot code loading, at least for the forseeable future). I'm not sure where you got the idea that Firefly throws away OTP, or tries to implement Erlang with different semantics, because that is explicitly _not_ the goal.