I think that's a misreading. That clause only limits additional fees charged to existing users for access to the source code. You can make the changes and char

I think that's a misreading. That clause only limits additional fees charged to existing users for access to the source code. You can make the changes and charge whatever you want for the software. When the user requests the source code, as is their right, for that you can only charge the physical costs. The intent is to prevent expensive source code fees from being used as an end-around the source disclosure requirements. It also makes sure the distributor can cover the cosrs, but no more than that.