I am calling their bluff that "Nxt is open source".
Rest assured, we have in the wings a better version.
Their? No one'd say such thing. More correct description will be: "Base code of Nxt (classes of objects, datathreads) went public 3rd of Jan, 2013, new features're testing as closed source, but anyone can decompile Java binaries and take a look, cos it isn't obfuscated".