If no specific license was mentioned then by default it's "All rights reserved". Which means the tutorial authors hold all copyrights povided by law. You are not allowed to do anything with the work (distribute, copy etc.)
Technically speaking...by you posting information you assume rights to the content or expressed consent from whatever author and you also grant xenforo the right to keep the information on their server, that is inherent.
But if I post something that is a complete reference to a subject and do it for free and someone else is going to make money simply for translating it or someone else is going to post it to boost hits to their site, the least they could do is compensate me for the time by at least asking me if they could copy my work and assume it as their own, or post a link back to the original document or something, even a genuine thank you would be a step up from how a lot of people fail to show some real appreciation to the people who help out for free and help spread the notion of appreciation for those individuals....
I just typed all that to explain something that I don't care about for myself for the most part.
It can not be that tedious to: start convo -> ask permission to translate with a link back to orig doc .... consider how long they spent to formulate a description in text and screenshot and crop or edit images and format up a nicely readable post for you to follow when it matters...and then ask yourself if fifteen seconds is enough time to spend asking someone if they mind that you redistribute their work or modify it.
If it is 50 different people , yes you need to ask 50 different people unless they express that this is free for public use in any legal way. Each person is an individual and each is entitled to at least a little bit of respect dignity and honor.