But if a UI works and is not copyrighted? I am against a scarcity mindset where we have to reinvent the wheel. Naoki has saved time and spent it more productively on the codebase and then released it as an OS product, good.

I agree, we shouldn't reinvent the wheel but it applies to "host of repositories" too :). There are already existing solutions so why spend time to build another one? Also when someone builds a product which does and look the same as another and even the name is very similar, it reminds me the Adidos(http://bit.ly/1aRN2IN) shoes. My point is at least make a different UI and choose a name which closes out confusion.

Adidos? I raise you with Lodidas :)

I know there are other solutions like Gitlab, but from what people are saying here, it is harder to setup & maintain, so I do not feel that this particular product does not bring something new.

Maybe create an open source GitHub/Bitbucket UI that people can use in their projects?

Heck they stole most of their name from BitBucket: https://bitbucket.org/features

And BitBucket was an attempt to steal GitHub's business primarily with Mercurial at the time, that Atlassian bought up, and since then GitHub has still been their #1 competitor, (not counting Sourceforge).

BitBucket and GitHub both launched in 2008, as far as I can tell. So I wouldn't say BitBucket was an attempt to steal GitHub's business.

Oh, come on. Bitbucket and GitHub both emerged at the same time; neither is a copy of the other, nor do GitHub's founders think that.