Got this answer from support, but I can't post it as an answer or in comments because I'm a nobody with no reputation:
Our app Handcent Next SMS has been misidentified as malware by Google, we are in talks with Google to get our app back to play store. In the meantime, please keep our app and do not uninstall. You should still have all your data when it returns to normal. You can use the stock app for now. Don't worry, we are trying our best to restore our service.