It has been a good week for fonts.
The London 2012 font been made available online at this link for download.
Open source projects wanting to evidence complete adherence to community developed technologies will want to use FOSS elements in their work from their programmers' shoe leather to the fonts used in the production of any written or textual elements.
This new free and open source font from Adobe is provided under the SIL Open Font License, which is classified as free to use by the Free Software Foundation.
Source Sans Pro actually comes in a total of six formats (or weights) and font author (or creator) Paul D. Hunt has said that the intention with here was always to provide a technology component that would be "production available" from the start.
Total open source font fans can of course visit SourceForge's FontForge, where you can find an outline font editor to build your own fonts or edit and modify existing ones with lots of cross-format convertibility.