Sufficiently Advanced has been released under the Creative Commons Attribution Non-Commercial 3.0 license. or 4.0 International for the second edition. The price has been reduced to a very minimal one, enough to cover hosting fees and printing costs.
You can find print-on-demand editions at those same links. Right now it's all in greyscale. Additional artwork is currently in development, and once it's ready there will be full-color versions available.
Those interested in a physical copy can find it at Lulu. You have many options:
If you're not sure if you want the first edition, why not check out the demo?
If you're a big fan of a particular civilization, or of our beautiful cover, you can find prints and other items at our DeviantArt store. Want a Disciples of the Void coffee mug? A postcard from Mechanica? We have a bunch of different items for sale.