WhatsApp has sent a lawyer letters to developers of Android apps who use the notifications of the chat app in their own apps. According to WhatsApp, the apps do not have the right to function that way.
Except the developer of Direct Chat that WhatsApp- conversations such as Facebook Messenger, the developer of Can not Talk has received a letter, writes XDA-Developers . This app uses the same api to allow users to automatically answer WhatsApp messages when they are in the car or in a meeting for example.
It is unknown how it will proceed now. It appears that the letter contains incorrect assumptions about how the apps work, and it is unlikely that WhatsApp could prohibit other developers from communicating with WhatsApp notifications via Android standard APIs.