Free Minecraft account users won’t be able to guarantee keeping their user names unless they the game by June 3rd. Mojang Support Manager Marc Watson tweeted the news today.
If you’re sitting on an unpaid Minecraft username, upgrade before June 3rd or you may not be able to upgrade it later help.mojang.com/customer/porta…
— Marc Watson (@Marc_IRL) May 29, 2013
Originally, you signed up to Minecraft with a free or paid ‘Minecraft account’. With this, you logged in with a username and password. Mojang is migrating people to newer ‘Mojang accounts’, which require you to log in with an email address and password.
If you have a free account, you could lose your username if you don’t migrate to a Mojang account before June 3rd. You can not get a free Mojang account – you only get one if you buy Minecraft. Paid accounts will also have to migrate, but there is no chance of losing their usernames. After June 3rd, if someone buys Minecraft they will be able to register with your free account username, meaning you won’t be able to have it when you buy the full game.