Do you intend to open source the code for this plugin? Perhaps under the MIT License? ;-)

According to the project on bukkit dev it is under the GNU General Public License version 3 (GPLv3). http://dev.bukkit.org/server-mods/multiinv/

The above is correct, though technically I'm meant to provide a copy of the License in any distributed copies of the source. I'll add a link at the top of each page of source eventually.