Well, it's a modded version of whatsapp, so there's no telling what malware, tracker, data mining crap that it may contain.
Good luck brother

 

This is an unofficial, bootlegged version of the WhatsApp app. WhatsApp is a commercial interest and its software is proprietary. As such any 'unofficial' builds are legally not compliant.
So by definition there is no 'reputable source' but generally the safest place to obtain an untainted APK would be directly from the app's developers.