Can I use apple's new font San Francisco for commercial use?
Nope. Not even a little bit. Unless your commercial project is a apple watch app.
A. Limited License. Subject to the terms of this License, you may use the Apple Font solely for purposes of design and development of applications for the Apple Watch. The foregoing right includes the right to show the Apple Font in screen shots, images or mock-ups of an Apple Watch application.
You may use this Apple Font only for the purposes described in this License and only if you are a Registered Apple Developer who is part of an iOS Developer Program team, or as otherwise expressly permitted by Apple in writing.
B. Other Use Restrictions. The grants set forth in this License do not permit you to, and you agree not to, install, use or run the Apple Font on any non-Apple-branded hardware or to enable others to do so. Notwithstanding the foregoing, you may use the Apple Font in depictions, digital and/or print, of the Apple Watch, but only for purposes of designing or developing applications for the Apple Watch.
Except as otherwise expressly permitted by the terms of this License or as otherwise licensed by Apple: (i) only one user may use the Apple Font at a time, and (ii) you may not make the Apple Font available over a network where it could be run or used by multiple computers at the same time. You may not rent, lease, lend, trade, transfer, sell, sublicense or otherwise redistribute the Apple Font in any unauthorized way.
I'd say the answer is "Yes - if you're making an Apple Watch app, or something for Apple Watch"
At least that's how the license is worded. Worth noting that they do mention you can use it if you're depicting an Apple Watch - you don't have to be actually making an Apple Watch app.
..Hey, at least he asked. :P
if you are okay with DMCA's cease and desist order :)
So as everyone else has said, the license agreement you agree to when downloading explicitly says its for Watch apps only.
With that said, all of the default apps (and some others) are using San Francisco on iOS9. When developing for iOS is there a declaration for using the default system font? This could be a great workaround to actually still use San Francisco once iOS9 is released.
Edit: Apple just released this: https://developer.apple.com/fonts/
I think no, except you bought the license maybe...