As it is now, JQuery UI does not recognize the library. To that end, it should be as simple as creating a symlink from /sites/all/modules/jquery_ui to /sites/all/libraries/jquery.ui thus:

$ cd ~/firstsite.com/sites/all/modules/jquery_ui
$ ln -s ../../libraries/jquery.ui jquery.ui
$ cd ~/firstsite.com/sites/secondsite
$ drush pm-enable jquery_ui
Module jquery_ui don't meet the requirements to be enabled.          [error]
There were no projects that could be enabled.                        [ok]
The jQuery UI plugin is missing. Download and extract it to your     [error]
jquery_ui module directory. (Currently using jQuery UI Not found)
An error occurred at function : drush_pm_enable                      [error]
$ cd ../firstsite.com
$ drush pm-enable jquery_ui
jquery_ui is already enabled.                                        [ok]
There were no projects that could be enabled.                        [ok]

This method works fine for the main site, but is not recognized by other sites in a multi-site install. By drush or by drupal interface, the jquery.ui library is not recognized or found by satellite sites in the install. For instance /sites/secondsite.com would not be able to take advantage of jquery.ui with the symlink.

I wish I knew enough to be more useful, or I'd have a go at it myself. All I am able to do right now is point this out in hopes that some very-informed person will put this on the front burner along with a fix for the missing library integration for jquery_ui: http://drupal.org/node/489140

Comments

Same thing for me.
I guess I'll try to copy the whole libraries/jquery into each multisite, but that seems silly...

I got this to stop complaining by re-re-re-reading the sites/all/modules/jquery_ui/README.txt

In particular, *inside* sites/all/modules/jquery_ui/ you need a symlink to the actual jquery library, and the symlink must be named jquery.ui:

ls -als sites/all/modules/jquery_ui
...
CHANGELOG.txt
jquery.ui -> ../libraries/jquery.ui
jquery_ui.info
...

Note the "." in jquery.ui for the name. Woof.

This stopped Drupal from complaining, at least.

No promise it actually works.

I'm just the back-end guy, and don't now how to test it.

This thing needs a settings page where I can pick the directory for it or something.