Is Minecraft Windows 10 Edition licensed per computer or per user?

I want to buy Minecraft Windows 10 edition for my kids. If I buy it one time in the app store and install it on my computer, will it be available to all users on that computer? Or do I have to buy it separately for each user?

NO, it will NOT be available to other users on the computer.

I have Minecraft Windows 10 Edition and unfortunately it's only for one user - the buyer. If You will log to the other account on the same PC it won't be available for second user. According to this link: Minecraft on multiple windows 10 PC logins

A game bought on Microsoft Store is available on multiple devices but only for the user account which bought it.

Even if you share the pc with other persons, they cannot play with your game on their own account. They can play on your account or they need to buy it for their personal account.

And I'm facing the same problem as You.

Actually, according to PC Gamer, you can share your Microsoft store game library with your family, including Minecraft. You can also play simultaneously on different devices.

You have to create a family group from your Microsoft account and add your kids to the family group (it can be done from Windows settings). They must have their own Microsoft accounts.

After the family group setup, it will be possible to download Minecraft in the other accounts.

It worked in my case (I was already managing my son's usage of computer and Android phone with a family group). I bought Minecraft using my son's account (I did not know the trick then), but I can download it using mine.

If I buy it one time in the app store and install it on my computer, will it be available to all users on that computer?

Yes, it will be available to ALL users on the computer. When you purchase an app, you're merely buying the license to download it. Once downloaded, it can be used on any device by any user on those devices, similar to the Android and iOS app stores. What you won't be able to do, however, (without being logged in with an account that owns a license for it) is update, buy an in-app purchase or re-download it.

tl;dr — Can play, but no updates.

Fun fact: This is also how pooled accounts work (multiple people share an account and the split the bills on apps).