HI,
Most of the package change log is maintained by community.
So best way to find the changes for a specific version of package is to look into the change log provided for that version.
Are you looking for source code of a package .
Source code of packages are also available in the form of RPM. https://public.dhe.ibm.com/aix/freeSoftware/aixtoolbox/SRPMS/
In case , you are looking for community link from which package is built, For most of the packages you can find the info from package spec file at https://public.dhe.ibm.com/aix/freeSoftware/aixtoolbox/SPECS/
The entry in spec which can tell you the community link looks like below.
Source0: https://ftp.gnu.org/gnu/bash/%{name}-%{version}.tar.gz
Thanks
Ranjit