The Community US Stamp Album uses an open source font from Adobe called Source Sans Pro. Adobe renamed this font to Source Sans 3.
According to Adobe, this is a “breaking change,” meaning, if you have any documents that use Source Sans Pro, they will not automatically switch to Source Sans 3. You’ll get an error that the font is missing. If you’re using style sheets in your apps, you’ll just need to update the style sheets and your document will be fixed.
The change only really affects anyone who’s editing my Scribus files. I’m working on the 2006 supplement now, and needed to make the switch from Source Sans Pro to Source Sans 3.
The two fonts look IDENTICAL, since this is just a name change on Adobe’s part. Here’s hoping when version 4 of the font comes out, they don’t rename it to Source Sans 4.