This app is not signed, follow the directions below to open it:

1. Copy PenPot.app to your Applications folder.
2. Open Terminal and paste the following:

sudo xattr -rd com.apple.quarantine /Applications/PenPot.app

sudo codesign --force --deep --sign - /Applications/PenPot.app

3. Double-click the PenPot.app to open it (you may not be able to open it)
4. Right-click the PenPot.app and select "open" (this time it should ask you if you want to open it)