The program: Senuti-free.dmg
Complete source code: senuti.zip
The author of Senuti distributed copies of it for years under the GPL, which states: "For example, if you distribute copies of such a program, whether gratis or for a fee, you must pass on to the recipients the same freedoms that you received. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights."
Please see this blog post for further discussion about Senuti going closed source.
Note that Pod to Mac is another program that also copies music between ipod/iphones to Macs, which is free. However, it appears to be closed source.