Pawel,
Correct, I believe it is not available outside of Japan. This topic came up recently on the site (though I can’t find the post) with someone else was saying the same thing.
If you click “Sign-up for news button” on the theta360.biz site, it includes the following statement:
THETA 360.biz is only available to users located in Japan as of now. We are under consideration to expand our international reach. If you wish to receive updates and news notification from Ricoh regarding THETA 360.biz, please use this form to sign up.
It also says the same thing on the Support page.
If you’re looking for alternatives, there’s a long list of virtual tour software in the List of RICOH THETA Apps.
And multiple real-world examples of business usage in the Business category.
Jesse