Regarding Julia, although the syntax is superficially similar to Matlab and we've intentionally made many things compatible, Julia isn't really modeled on Matlab. Julia is much more influenced by Lisp – much like Mathematica via Macsyma and Maclisp. Julia's dynamic multiple dispatch is somewhat reminiscent of Mathematica's pattern matching dispatch system too, although, of course, the evaluation semantics are radically different.
I hate to quibble, but having a web frontend for Mathematica that you don't charge people to use does not make it "effectively" open. Mathematica is a shining example of excellence in closed-source software and I have no problem with it as such, but calling it "open" because there is a web version is just disingenuous b.s.
[1] http://www.wolfram.com/products/mathematica/newin7/content/D...
[2] http://www.wolfram.com/mathematica/new-in-8/probability-and-...