The temporary files are not located in a fixed location but in a dynamic generated nested sub folder of /var/folders.
Open this folder in the Finder by following these steps:
To remove all Download Buddy data from your Mac, you'll need to delete the local Sandbox container folder:
Download Buddy is still work in progress so the current version of this app will certainly not be the last version. Useful new features and enhancements will be added in upcoming versions of the app. Version 1.9 of Download Buddy contains the following known issues, which are to be solved in one of the upcoming versions: