Nah; regular old Lua 5.1. The colon syntax is just syntactic sugar -- self isn't actually bound.

function Foo:Bar(baz) is the same as Foo.Bar = function(self, baz); invoking Foo:Bar("rebar") is sugar for Foo.Bar(Foo, "rebar"). self is never bound - it's just passed in (explicitly, via . syntax, or implicitly, vs : syntax). In all cases, the caller is always specified.

You can pass Foo.Bar around (as it's a function reference), but if you have something like:

    Foo = {}
    function Foo:Bar(baz)
        print(baz)
    end

    local baz = Foo.Bar

Then baz has no binding information to Foo; defining the function with the : syntax is just syntactic sugar. To invoke, you would have to call:

    baz(Foo, "woohoo")

Just calling

    baz("woohoo")

populates self with "woohoo", and the bar parameter would be nil, demonstrating that there is no contextual binding to the function itself.