SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
The OFL allows the licensed fonts to be used, studied, modified and redistributed freely as long as they are not sold by themselves. The fonts, including any derivative works, can be bundled, embedded, redistributed and/or sold with any software provided that any reserved names are not used by derivative works. The fonts and derivatives, however, cannot be released under any other type of license. The requirement for fonts to remain under this license does not apply to any document created using the fonts or their derivatives.
It seems like a silly restriction anyway. What advantage would someone gain over Adobe by selling freely available fonts "by themselves" with no added value?
"The following restriction on distributions, which is part of OFL, has been widely accepted by open source projects when it is applied to fonts:
1) Neither the Font Software nor any of its individual components,
in Original or Modified Versions, may be sold by itself."* 
The price it sold at. Just like people sell public domain texts, or even chunks of wikipedia as Amazon ebooks, with no added value.
The only added values I can think of would be the traditional reason why people used to buy CDs with freely available software:
- the seller delivers the stuff cheaper than if the buyer downloaded it themselves (highly unlikely nowadays, but maybe there are corners of the world where this still applies)
- the seller acts as a curator, sifting the gold from the junk, so that the buyer need not do that.
The 'curator' role might still be worth something. For example, a site could have a link 'do you like the template/icons/font we use? Buy it here'. That would be forbidden by this license (but selling all three in a package, or even two fonts with this license in one package, would be fine, at least in a literal interpretation of the license)
The TypeKit page is a decent substitute, anyway: https://typekit.com/fonts/source-sans-pro
Not a bad News Gothic descendent at all. It takes News Gothic's structural personality and adds a bit of Frutiger's humanism.
Free fonts usually come in one width, two weights (regular and bold) and two styles (roman and italic), for a total of four variations, and usually cover the Latin alphabet plus a few relatively-common variants (accented characters for western European languages, and maybe a couple of additional characters like the the German eszett or the Icelandic eth).
Professional fonts will often come with perhaps five weights (light through black), three widths (condensed, normal, wide), and two styles, for a total of thirty variants. Some will also come in different optical sizes, or have other variable properties. Additionally, they'll have much larger character coverage (perhaps including Cyrillic or Greek), and have multiple stylistic variations of individual characters (stylistic alternates, swashes, old-style figures, etc.), as well as ligatures of commonly-colliding pairs of characters like "fi." Professional fonts can thus have literally thousands of times more glyphs, are very labor-intensive to produce, and are fairly expensive.
This font is certainly less rich than most of Adobe's "Pro" line of fonts, but still looks much better than a lot of what's out there in terms of open source type.
For example, the most popular sans on GWF is currently Open Sans, which does come in a wider range of weights and has italic and condensed versions available. Unlike this new font family from Adobe, Open Sans also renders well on Windows, including Windows XP and including all major browsers when used as a web font.
On the specimens there, Source Sans looks terrible at almost any sensible body text size in Firefox on Windows XP.
However, I was comparing those results with samples of Open Sans from Google Web Fonts, which look much better. Apologies if this wasn’t a fair comparison.
That really made me laugh. I love it! :)
Is there a lack of cookie recipes?
Here's the download link:
With only a quick look this looks like a really helpful contribution. I wonder if the name is a play on Open Sans.
(and the monospaced version)
I ask because I didn't notice any zeros in the code example.
[[On an aside, I love this thread. A post about the license, geeking out about the font and even more specifically the monospaced fonts. No where else would I see this conversation. :)]]
edit: sorry to burst bubbles, the release/source doesn't include the monospaced variant yet.
At this point, however, GitHub is a far larger organization. They host an order of magnitude more projects.