Can Minecraft be played on different machines?

[pidget]

My son is really keen to get Minecraft, my only concern is that we have 3 different pc/laptop combinations at home so does he just have to play on the one he downloads it to or can he play anywhere with the right password/information??

[AB Editor]

If he's playing it online with others it doesn't matter where he is. Equally, if he's playing in the browser it'll save his worlds.

However, single-player in the downloaded version will only save to a single PC. One suggestion is to change the save file location to somewhere on your home network which can be accessed by all machines, or to copy the save file data across to a usb stick and have him move about with it :)

Although, I've only just read your question properly:

Yes, he can log in anywhere with those details, he won't have to purchase it more than once and he will always be able to download it again as long as he can supply his details.