Times ago I developed a MultiSite Wordpress installation, and now I want to move it from the main root folder to a subdirectory.
Is it possible run an MU version of Wordpress in a subfolder directory?
Yes is possible. The only thing is that you will have "two sets" of permalinks:
Here is a codex article that explains that.
Edit 1: Here is a more detailed article on the topic with it's pros/cons and potential issues.