Such information is recorded in the project:
https://sourceforge.net/projects/jfreechart/
You can browse the subversion repository:
https://jfreechart.svn.sourceforge.net/svnroot/jfreechart/
You can examine the project's revision history:
svn log https://jfreechart.svn.sourceforge.net/svnroot/jfreechart/
You can check out a local, read-only copy of the subversion repository:
svn co svn://svn.code.sf.net/p/jfreechart/code/trunk jfreechart-code
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