Although both plugins are free, Pro is managed directly on Symbiostock.org with regards to downloads and updates. Lite is available directly via WordPress.org. Lite is a GLP licensed product, whereas Symbiostock Pro is a proprietary commercial software that is Non-GPL licensed (see Licensing).
1) Lite serves as a WooCommerce extension for users that just want to use its functionality for personal, non-professional use. It is simple, easy, and adds very little overhead to your system. It allows you to upload images which are watermarked and added to your store in real time. There is no processor, no licensing, and you must manually alter pricing and publishing.
2) Pro is an upgrade to lite that adds a whole world of professional features, such as licencing, custom watermarks, FTP uploads, Symzio integration, and more. As well, all of our premium plugins, such as the video and submitter addons only function with Pro.
1) Symbiostock Express will function with both plugins.
2) Symbiostock Pro requires Symbiostock Lite to function.
3) Symbiostock Lite products are not compatible with Symbiostock Pro. It is strongly recommended you upgrade directly to Pro if you are a new user so that you do not have to upload media twice.
Why the split? We want to provide users a simpler version of Symbiostock so there is less overhead, and by hosting Symbiostock Pro directly on Symbiostock.org we can optimize how the plugin is distributed and downloaded without having to interface with any third parties.