I think that when you're publishing translations then, at a minimum, you should make clear at the top of the page that it is a translation, provide a link to the original, and include the author's name or username. You should also make a good faith effort to seek permission from the author.
If the article you're translating was itself translated from an original source, then "author" here means author of the original material. The latter would seem like an obscure edge case, except that some of the translations you published actually were that.
We want solid content on HN, so I'd like to find a way to have these posts not be a problem. No doubt the community will scrutinize future posts, so we may have this discussion again, but for now we won't ban the site if you do the above.
Original articles, of course, are more than fine. One problem with grey-area tactics is that they make your whole site look shady. Readers will think that all your articles must be hijacks, whether they are or not. To pick one example that was posted to HN, who wrote http://kukuruku.co/hub/mobiledev/mobile-typography? It's not clear whether this content was created for your site or stolen from elsewhere; besides which, readers want to know the names of the authors they're reading.
If you attribute everything clearly and prominently, this should go a long way toward clearing things up.
Hasty Edit: Googling reveals that you copied the mobile typography content from http://my.safaribooksonline.com/book/programming/mobile/9780.... That's disgusting, and certainly explains why you omitted any attribution. If you keep doing it, we'll ban your site, despite our fondness for translations of obscure but solid Russian technical articles.
It's in your interest to pay attention here. You have first-rate, highly technical HN users like nkurz, acqq, and jacquesm—plus a site moderator—bending over backwards to help you. If the material on your site were merely the usual blogspam, none of us would care. We're putting time into helping you because we want access to the solid material. There's clearly demand for top-notch Russian articles in English translation. On the other hand, none of us has patience for yet another shitty hijack outfit on the internet. You can't be both; not here, anyway. Please turn this into a positive by listening to the community feedback and cleaning up your act.