Alternative GUI shells can be developed for Windows, their usefulness however would be severely limited if they couldn’t incorporate extensions written for Windows’ default GUI shell, Windows Explorer.
I only know of one GUI shell replacement for Windows which fully supports the standard shell context menus for files, folders and multiple selections of files and folders (including third party entries into these context menus, like the ones from TortoiseSVN), and folder background context menus (right click on a folder’s background), xplorer² (XYplorer looks like an xplorer² clone, but it seems it isn’t. It supports icon overlays, but not namespaces, yet). Total Commander (and/or FreeCommander) might also offer this functionality, but I have not yet seen this functionality in it. (However I do not know wether these two tools display third party namespace extensions like their are used by web.de and others.)
The problem with writing a GUI shell replacement is not only the size of the task. You have to implement drag and drop, efficient file copy, and a lot of other things, but you also have to support shell extensions that display custom entries in context menus, icon overlays, namespaces, etc.
As if that wouldn’t be large enough a job, you also have to know your way around C++ and COM, because that is what shell extensions are (typically) written in, and those aren’t trivial, at least not in my opinion.
Because this is how things are, it takes people with considerable knowledge to write a replacement shell.
Would shell extensions be implemented by simpler basic mechanisms and languages than C++ and COM even application developers might manage the task.
Speaking of which, which standards for GUI shell extensions exist on other platforms? If any, how complex is the task of simply implementing a shell extension for example for displaying a few custom icon overlays (does the shell support icon overlays in the first place?) or a namespace (like Windows Explorer does)? Shouldn’t the Unix/Linux world define a few simple mechanisms/standards for things like this so there is at least a remote chance to write a GUI shell extension like TortoiseSVN that can be used in any full fledged GUI shell for Unix/Linux?
(PS: Possibly related: 15 Windows Explorer alternatives compared and reviewed)
