i bookmark is based on an open-source project licensed under the GNU General Public License. This means you can host it on your own web server for free, whether it is on the Internet, a private network or just your own computer.
i bookmark supports most of the del.icio.us API. Almost all of the neat tools made for that system can be modified to work with i bookmark instead. If you find a tool that won't let you change the API address, ask the creator to add this setting. You never know, they might just do it.