The bukkit project page for RestockIt is available at http://dev.bukkit.org/server-mods/restockit/
The source code for RestockIt can be found there, and alongside the class files in the compiled jar.
RestockIt uses the GNU GPL v2 license. See "LICENSE" in the same folder as this file.

Copyright (C) 2011-2012  Chris Price (xCP23x)

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.