Unless you are talking about uploading Russian-language books, all that matters for copyright purposes is the copyright status of the particular translation you are working with - a translation has its own copyright status, independent of that of the original work.
If a book is uploaded here, it is only the copyright status in Canada or the US that is relevent, not the copyright status in the author's own country. Our primary server is in Canada, which has a "life + 50" copyright law. It is irrelevent whether or not the work is in the public domain in any other country.
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