You may ask why. Well, the reason is simple: Oxide is available for Windows only (depends on VC Redist 2012 x86 - see http://forum.rustoxide.com/resources/oxide-server-mod.3/ ) and new features / bug fixes depend on a static group of developers.
So this is a call to developers with access to the Rust server software: Go start working on some kind of open-source Oxide. It should just give LUA developers an API, build-in plugins are not required (and I think shouldn’t be there anyway). I would do it for myself but I’m a C++ n00b and don’t have access to the server software.