[cobrabyte]

They didn't open source Swift out of the gate because they wanted to guide its development according to the features and plans they had for the language. Wanting to have a firm grasp of the language's core features and implementation is reasonable. After all, I believe Lattner was unhappy with some early directions they took with Swift, but it was too late to change anything because libraries and such had already been written. I may be fuzzy on that, but that's what I seem to recall.

Also, I am not an absolutist where free software is concerned. It doesn't make the world worse to release proprietary software. Especially if you have the stated goal of eventually open sourcing it.