First, thanks for the donation.
According to our records, you paid with e-check which essentially means that you make a bank transfer which takes a few days to complete. For the online shop service which we use it means that payment is not yet completed (and yes, it appears for us in the shop interface as "pending"). You may want to add a credit/debit card to your PayPal account to avoid such misunderstandings in the future.
Now, about the download: you can download the same GanttProject at any moment for free from our download page by clicking "Just download without donation" link.
If you still would like your payment to be refunded, please let us know.