I cannot create an bustadice account
Invalid user name. error message is showing up

whatever username I would like to choose

And I've tried in 3 different browsers :|
Unfortunately I'm not able to reproduce that. What user name are you trying to use? Is it possible that the name is actually invalid and that the error message is not a bug?
In case you are still wondering what was the reason of my problems I can tell you ... I mistook SIGN IN with REGISTER button

I'd like to join their signature bounty; but account is required to do so

BTW what are conditions of withdrawals in bustadice? Any kind of verification, KYC AML or so?
Bustadice doesn't require KYC when you're about to withdraw your funds. Mininum withdrawal is just 100 bits and fees varies depending on hows network the situation.
See it for yourself, it's easy to use and user friendly.
Thanks!
Does Bustadice has any faucet or another way to try the platform before depositing ?
I have investments in all four (minus Bitvest) and both busta-sites have been much more profitable than the other two.
What kind of investments are you talking about? Can I deposit money to bustadice/bustabit to earn interest?