Someone at some point may notice that CSV 2 POST has three CSV file upload scripts, that are all the same. Well as I type this they are. The plan is to adapt each of them for different purpose. It is also handy for hacking because we can keep an original script.
Free edition will obviously end up with something more simple compared to paid edition also. So this is the reason for duplicate code, which is not normally the done thing.
The ECI screen for paid and free editions each have their own script. The sandbox areas CSV file upload form uses a different script also. That one will become the most advanced and will be modified to allow other file types. The general form submission processing for the sandbox area will actually process other feed types being submitted for the initial setup such as URL or FTP etc.
For now they are just duplicate code!