This PowerShell script will generate a Windows form Which will allow you to retrieve the sources of your packages from the SCCMContentlib folder.
It will restore your files in a folder with the name of the Package ID in C:\Temp. To modify the path, change the variable $temppath at the beginning of the script.
When you lanch the script, enter a package ID and click on "Check info" to recieve only informations, or click on "Regenerate" to restore the sources:
When it is regenerated, you will find the sources under "C:\temp\PackageID":