Developers have reported that apps made using Electron, a cross-platform desktop app making framework, are being rejected by the Mac App Store.
The automated review process is rejecting the apps on the Mac App Store because of their use of private API calls.
A private API acts as a front end interface to back end data and application functions. The API calls are part of the underlying Electron framework, and are not part of the apps themselves.
The Electron framework has always had APIs, but Apple has recently upgraded its review processes to identify policy violations, as noted by 9to5Mac. This has caused the private APIs to be detected.
Although it does not seem that Electron is doing anything that would be considered malicious, review processes generally don’t care why an app is using private APIs.
Developers can choose to publish their apps independently if they choose not to submit them to the App Store. They would still need to be notarized through a developer account, which ensures that it can’t be tampered with.