Not directly, but you can get something very similar:
In the search page, select the "E-Book Uploads" forum, make sure the "Also search in child forums" is ticked. Write the user name in the top right box, and select "Find Threads Started by User"
Or, in the "
E-Book Uploads" page, click on the "Uploader" header, and it will be sorted by uploader. Now you just have to find the page where the desired uploader appears.