This app is not an official google product. It is developed by a single programmer using the APIs provided by google. The intention is to make Google Tasks easier to use on big monitors.
It is distributed either as a website at https://fullscreen-for-googletasks.com or as a chrome extension at https://chrome.google.com/webstore/detail/full-screen-for-google-ta/ndbaejgcaecffnhlmdghchfehkflgfkj.
You should only use this app in the two ways mentioned above. Do not use if it's distributed from other sources, as it could be altered.
It does not use an open source license, and the author / publisher holds the copyright. Do not redistribute this app, completely or partially, with or without modification.
This app is provided without warranty. In no event shall the author / publisher be liable for claim, loss, damage or other liabilities.