The build of PingPlotter for OSX you're attempting to download is unsupported and deprecated. For more information, see here.
If you absolutely must have the old build (which has UI issues on Yosemite, can't open current .pp2 save files and is not recommended), you can still download this one.
You'll need a PingPlotter Standard or PingPlotter Pro license key to make this version run.
Note: Download instructions will be emailed to the address you specify. Without these instructions, you cannot download the software.