From the pdf Flip For Mac user guide, which comes free with the software:
System Requirements Mac OS X (on Intel or PowerPC) Version 10.3.9, 10.4 and higher QuickTime Version 7.0 and higher Installing Flip4Mac WMV Flip4Mac WMV software is distributed as an Internet-enabled disk image file. When you download it, Safari automatically mounts the disk image and runs the Flip4Mac WMV installer. Follow the instructions in the installer to complete installation. If you are using a different Web browser or you received the software on CD: 1. Double-click the disk image file (Flip4Mac WMV.dmg) to mount the disk image. 2. Locate and launch Flip4Mac WMV.mpkg, the installer file. 3. Relaunch your Web browser and QuickTime applications. Note: You must restart your Web browser and all QuickTime applications for Flip4Mac WMV to work correctly. Also, you must provide an administrator name and password during installation. If you installed Flip4Mac WMV with a QuickTime application open, you should reboot your Macintosh before using Flip4Mac WMV