First some background info:
In the major refactoring from EPiServer CMS 4 and EPiServer CMS 5 we integrated the editor more tightly with the UI. There were two major changes that affects how the editor can be used outside the UI. One was to move many files into the "ui" folder that is normally protected by path access rights in the web.config file. The other was to rewrite how popups are handled to enable support for other web browswers than IE.
With this in consideration, the editor in EPiServer CMS 5 is written to work when having access to the ui folder. It's possible to get it working by allowing access to certain parts of the UI as described in the section below. We have also had some bugs where we did not take into consideration that the editor could work outside the normal editor environment but these have been fixed to the SP2 release.
Here is a more detailed walk through of how to get the editor working outside the UI:
Enable edit mode for the property:
Add a css class in your style sheet for the cover dialog that is used for popups:
EPi.Dialog cover class
Enable access for the required files in the UI for non-authorized users:
Step 2 and 3 wont be needed in EPiServer CMS 5 SP2. Regarding the access to files in step 4 this enables most of the files needed but you still might have to give access to more files depending on what functionality you want to enable in the editor. For instance, the file dialog requires files from the /ui/edit/ folder.
I hope that this information is enough to understand how the editor works and how to get it working in your sites.
EPiServer Development Team
ps. I know that it's a bit strange that we have some properties that does not work out of the box when setting edit mode to true and not having access to the UI-folder. These includes long strings, datetime and page reference properties at the moment. We are aware of thisproblem and have a long time plan that all properties should work without any dependancies to the UI. ds.