Adobe reports: [edited]
We are pleased to announce the release of Source Serif, a new open source typeface which is now available here on Typekit — as well as directly from SourceForge, for anyone who feels inspired to dig into the original font files.
Source Serif was designed by Frank Grießhammer as the serif counterpart to our popular Source Sans family.
Adobe’s principal type designer, Robert Slimbach, consulted with Frank on the design of Source Serif, helping to ensure its compatibility with Source Sans. With its simplified, eminently readable letter shapes, Source Serif is well-suited for digital environments, and shines when used for extended text setting on paper or on screen.