Posting to the Steem blockchain requires a Steem account. This is necessary for access to the blockchain but also to allow the collection of rewards in a Steem wallet.
For the same reasons, any application that is built to access the Steem blockchain, whether Steemit.com, Busy.org, or Musing.io, will also need its users to have Steem accounts.
Most account registration is through the original Steem platform Steemit.com. Registering through other platforms is also possible but rarer. For example Utopian.io has a sign-up procedure but only for users with a proven github account and relevant open source history.
The creation of each account has a cost in Steem and a required level of Steem Power delegation, so it is not free. When users sign-up on Steemit.com they are effectively being donated this fee by the central Steemit team.
This leads to a battle for the account registration team to prevent sign-ups from scammers who seek to register thousands of accounts and gain small amounts of Steem Power with each account.
For other platforms, like Musing.io, allowing direct registration would shift this administrative burden to the Musing team and also have a cost, unless direct registrants were willing to pay a fee. As such this approach is rarely put into practice by non-Steemit platforms,
This situation will change with HF20 with an overhaul to the account creation system. Users (or the accounts behind platforms for example) will be able to create new accounts using Resource Credits instead of the current account creation fee (note: Resource Credits are the new system being implemented to handle bandwidth on the Steem blockchain).
As such, from September 25 we are likely to see changes with the potential that alternative Steem applications and platforms will start onboarding users and creating their Steem accounts directly.
That's because Musing uses the Steem blockchain, which it does not own or maintain, as the back end of the service. What it means that all of the content, questions, answers, upvotes and rewards are recorded as transactions on the Steem blockchain. Musing.io is essentially a user interface into the Steem blockchain. The Steem blockchain is used by hundreds of other applications. Anyone can use the Steem blockchain or build apps that use it.
Musing.io asks the users' permission to post their content to the blockchain using a service called SteemConnect. It does not control what happens in the blockchain. The rewards that they users get after the 7-day payout window belong to the users and controlled by the users themselves using a Steem wallet program. Musing can't do anything with them.
Musing.io works on the steem blockchain and it is directly connected to steemit when you post your question and answers it appears in the steemit blockchain of @musing account. The reward also appears in your blog in steemit in comment section or in blog section.
There is a requirement of steemit account if you want to work on musing else you will not get your account approved. Steemit account gets long time to approve it takes 3 weeks for approved or else you can go for small investment for your account.
All account which runs on the steem blockchain are interconnected to each other and the reward for all steem applications you work appears on your steemit section.