BY.COM.UA 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.
BY.COM.UA supports most of the del.icio.us API. Almost all of the neat tools made for that system can be modified to work with BY.COM.UA 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.