Satyajit well, you'll need to upgrade at one point...
If you're not very sure about what are you doing I advise you to wait an official release.
Flarum is a great product with great developers behind it. But, as all the open source projects, it's possible that one day some security flaws to be found. And if you'll leave your forum publicly available at the current version (0.5beta), you may get hacked one day and you won't like this. And it won't be Flarum's fault because, as luceos said : you can use it in production at your own risk.
I don't want to scare you, I just want to be sure that you understand the consequences of the thing that you said :
I don't need upgrade ?
