I made a SIMBL plugin
for Terminal.app which enable us to copy on selection.
Here is the plugin named TerminalCopyOnSelect.

TerminalCopyOnSelect.bundle.zip

INSTALLATION

1. At first, you should install
   SIMBL.
2. Download the zipped plugin file I mentioned above and expand it.
3. Copy the extracted file "TerminalCopyOnSelect.bundle" to the plugin directory which is located at ~/Library/Application Support/SIMBL/Plugins/
4. Terminate all processes of Terminal.app and restart it.

You're done!
Now you can get copied selected text from the terminal when you released mouse button on it.

You are also able to disable this feature by turning off the following menu "Copy On Select".

Finally, I opened the source of this plugin on the GitHub
under the MIT license.

• http://github.com/genki/terminalcopyonselect/tree/master

Enjoy!