You can try Geotag right now without installing it on your computer. You need to have Java SE 7 runtime installed. You can install it by clicking on this button:
Once Java 7 is installed you can use Java Webstart to launch Geotag. All you have to do is click here:
Using Java Web Start to run Geotag ensures that you always have the latest version with automatic updates.
Using Java Web Start does not mean that the application will be downloaded over the internet every time you run it. The executable will be cached on your computer and only downloaded again if there is a new version available.
Please use the program on copies of your photos for a while. This software is still new and may have bugs.