It might take only 30 sec to tweet about it, but with open-sourcing comes a lot of stuff to deal with: once it goes open, there will be forks and pull requests and what not. Apple probably isn't yet ready to do fully open development (like they do with LLVM) of Swift.
Did you not actually read the comment you replied to? The entire point was that they haven't even said "We intend to open-source Swift once we're ready." The last we heard, they hadn't even considered open-sourcing it, like, ever.
(To clarify for people who like to misread things, I did not just say "They expressly intend to never open-source it." I said that, last we heard, they had not even talked about ever open-sourcing it.)
Why should they waste 30 seconds on that? To satisfy you? Very few people really care about this. If they say anything and then it takes longer to deliver than they thought those people will jump down their throat. Better to say nothing and announce when ready.
