Hello, @yebellz thank you for taking the time to write all these suggestions. 
Let us see what can be done :
Currently, the book has been written by one person, and seems to have a sense of finality in terms of its content
I am very open to suggestions, corrections and additions, but at this moment as far, as the content is concerned, I have received feedback that is a bit confusing to me (e.g. some say the book is too long, others say it is too short, other say it is too simple, others say it is too complicated, you get the picture
) and I really cannot see how I can adress all those contradicting matters … what I am certain off is that whenever someone spots a mistake (be it in the text or the diagrams), I can and do correct it immediately. I have no confusion there.
And there are quite a few of those mistakes, mostly minor grammatical ones ( an “is” missing here and there or a sentence that needs some restructuring) and a couple of wrongly numbered diagrams and things like that. If anyone finds any of those or thinks that I am talking nonsense at some point, please send me the mistake and I will fix it immediately .
I recommend that you look for collaborators that not only help you with translations, but also toward improving, editing, and expanding the content. Perhaps, the project could even evolve into a community-driven effort to produce public content.
It could, and I certainly hoped that this would have been the case, but unfortunately there doesn’t seem to be enough people that want to do such a thing. And I do understand why someone wouldn’t really want to invest his time on it. Written by some obscure SDK and requiring free work, is not exactly something that would have people rushing to help 
Back in December when I launched the website and asked for feedback and suggestions on how to organise the translation, there were some very good ideas and I tried to implement a lot of them (e.g. creating a cloud environment where we could all access the file and translate live OR installing Pootle like here in OGS and stuff like that) I poured a lot of time into it, but in the end of the day things couldn’t work due to my cheap website package. The company told me that if I wanted such lofty stuff, I should go and take a VPS, which I couldn’t do at the time.
I was a bit disappointed that I couldn’t provide the best service, so by January I decided that Google docs would have to do for the time being and depending on how things went, I would have given the money to get a VPS and do all that flashy stuff. I think that most people would agree that this is a reasonable “one step at a time” way of thinking 
To cut a long story short, at this moment there are only a couple of people working on this project and only for a couple of languages and I am very thankful to those people because even long established places like Sensei’s do not seem to have too many contributors nowadays, so I am happy that there are people willing to help. But I really do not think that other people are not helping because the work is being done in Google Docs instead of GitHub, for example.
The project has a very small dynamic at this moment and that is the fact with which I need to work with and I need to improve a lot of other things first 
On the other hand, most commercial books simply state “All rights reserved” along with a statement prohibiting reproduction. I’ve never seen a book forbid general use.
As I said in the previous topic, this is my first book, so for the typical stuff I went along with the flow … I googled a “typical book disclaimer” and just put it there …
To give a better explanation since we are not derailing another topic here: I made those pages after finishing the English book and I was so glad to have managed it, and at the same time anxious to begin translating in Greek, that I didn’t really give much thought to such typical matters. I am an avid book reader, I have hundreds of physical books in my house and I never really bother reading the first “disclaimer” page, so it was just a page that had to be there, but I didn’t really give it much thought.
Obviously I was wrong 
In the next version upload (possibly by the end of this week), I will amend that.
Your copyright statement also asks people to share this book only by referencing the website, where they can download it. […]
Also, there does not seem to be much reason not to allow people just to share the file directly.
Well, yes, but there is no prohibition about it … it says:
“When sharing this book, please do so by referring to the original website, so that everyone can contribute to the embelishment of the available translations and the books provided.”
… of course you could just put it in a flash-drive and give to anyone, but if you are going to send it via the internet why not use the original link, instead of downloading it and sending it directly to someone else? Seems like simply sharing the ling is the most practical idea.
This could have scaling issues (if the book were to become popular) since it concentrates the bandwidth burden on a single website.
That is a big “if” that doesn’t seem like a possibility in the forseeable future … 
I did have a second - outside source - of downloading the books ( I had uploaded them to box.com ), but I took those buttons down when I uploaded the Portuguese first chapter because there was no need for them (and my uploading speed is horrible ).
You could add a page or two to the book in order to explain the aims of your project, which would avoid the need to point people to a web page.
I did, they are pages 1 and 2 in the book and most people seem to dislike them quite a bit, judging from the feedback I’ve received. I didn’t really want to clutter the book with the things I wanted to say or do … I wanted the book to be almost totally about Go (188 pages out of 192 to be exact), so that is what I did and left the explanations for the website.
The PDF file size is very large (250 MB for color, and 90 MB for greyscale). This could hurt distribution to people with poor connection speeds and/or costly data rate plans
I am one of those people and trust me, uploading takes hours … that being said I can download 90mb in an acceptable speed and considering that nowadays most people have gigabytes of music even in their smartphones, it really doesn’t seem that much size-wise.
I did try to create downsized versions of the pdf, but that really messed up the diagrams and made them fuzzy and horrible … I will see what I can do in terms of outputting a pdf in a smaller page size, but with a high image quality. That would reduce the file size, but inhibit the amount of possible zooming. I’ll experiment upon it.
Why did you bother to apply for an ISBN at this stage?
I honestly have no answer other than “all books have one”, so I thought that it was needed …
If you go to the website you will see that :
The ultimate goals of the project are two:
a) Produce more translations of the book, with the help of of other native Go players
b) Eventually have the funds to print some physical copies and give them to the Go associations of each country, so they can distribute them as they see fit.
so, if I was to print them, they had to have an ISBN … or at least that is what seemed reasonable at the time … needless to say that goal “b” was ( and proved to be) too lofty, but the groundwork for it was done either way.
Thank you very much for your time and your suggestions.
Have a nice day!