It's a neat little application that runs in the background and allows you to start drawing with a single press of a shortcut.

Yes, you can use iScribby for free. There is a premium mode available though, that unlocks additional features. It's currently available for free as well, but this may change in the future.

Yes, almost every action in iScribby has a shortcut which can be customized through the settings.

Yes, iScribby can render over pretty much anything, including full-screen video games.

Yes, iScribby allows you to draw over a live screen, instead of a screenshot.

No, iScribby is designed to be as unobtrusive as possible. It won't steal focus from whatever app you are using when you enter/exit the draw mode. That's partly why you can use it in full-screen apps like video games.

Yes, things you draw using iScribby can remain outside draw mode while you continue interacting with your screen. You can choose to disable this behavior though.

Yes, feel free to check the support page.

However many you need. iScribby provides a color picker without limiting you to some small set of colors like other apps.

Yes, you can change the background of the screen that's used in draw mode.

If you have app already running, check the tray menu in the bottom right corner of your screen in Windows. Right click on the iScribby icon and look for an option titled "Enter draw mode". It'll display the shortcut you need to press to enter draw mode. Or you can just click on the menu item, if you prefer using your mouse.

Currently as of writing this, iScribby supports Windows. With continued development this may change in the future and other operating systems such as Linux may be introduced, if there is enough demand.

Yes. As long as it's obtained from the official website, it should be all good. Here's a scan result from VirusTotal - link.

Yes, you can undo/redo most actions you perform on the screen.

No, as of writing this, iScribby doesn't collect any sort of telemetry.