If you have trouble downloading the German language files, you could attempt a manual installation.
To do that, you first need to download the German language pack at this link.
- For the Mac App Store, you will need to extract these to: ~/Library/Containers/com.inxile.BardTaleOSX/Data/Library/Application Support/The Bard's Tale.
- For all other stores, you need to extract these to: ~/Library/Application Support/The Bard's Tale
To enable the German language pack, you will then need to go in-game and select Options -> Sound, and change the language to German.