It's impossible for Steem to not be open source. Every node runs the code independently.

https://github.com/steemit/steem

Steemit used to be closed off, but that was two years ago.

https://steemit.com/steemit/@steemitblog/steemit-com-is-now-open-source

So I'm not really sure why you think these things.

Plenty of clones of Steem are around like Golos and Weku. How is that possible without open source code?