Install the module as usual, generally under your sites/all/modules folder. On a Unix command line, you can use the tar tool like this:
cd sites/all/modules tar -xf to_do.tar.gz
Then go to Administer » Site building » Modules and enable the To do list module.
Some companies create huge products and use DVDs. This is a good solution, but printing a DVD cost more than a simple CD. If you need a DVD only because of a few MBs, that can be quite upsetting since you will pay many extra dollars to press your products. Made to Order Software has a similar problem with downloads. A product for download should be as small as possible simply so it can be downloaded by many more people.