The free refers to the DRM - I'm perfectly happy to pay for my books, but the legal situation over DRM gives me hives. Free is also fun, of course.
So the bit about being able to read parchment that is 4000 years old is at best an exaggeration. (Do we have parchment that is 4000 years old? Last I'd heard much more than 3000 years old it's all bronze, or written on bones...)
The peroid of classical Chinese I am most familiar with is about 2,500 years old. It is a different language. The grammatical structure is totally different. There are individual characters that mean the same things, but there are also ones whose meaning has changed, not to mention a lot of characters that aren't in modern use. An educated Chinese person who hasn't made a particular study of guwen might be able to stumble through a guwen document from this period, badly - and that only because everyone gets a little guwen in school. (And I've certainly run across native Chinese speakers who don't seem to realize that writings from this period have different grammar, and they just look up the characters they don't know and produce the most appalling bad translations.)
But seriously, pretty much all my Chinese friends who I don't know from a guwen scholarship context are all "OMG, you read guwen? That's so hard!" And as I said, I rarely read stuff much older that 2,500 years.
Also, the scripts are different. I think most literate Chinese folk would be able to mostly muddle through the scripts from, say, 3000 years ago. Less sure about older than that.
Spoken language... So, we know that the pronunciation of words in the language was substantially different. My recollection is that there is a scholarly consensus that Chinese was non-tonal during that period I know best (okay, my modern is better, but of the older forms of the language) and there are a lot of reconstructions of what it did sound like - I don't know how accurate they are.
Five hundred year old chinese is a lot more modern... and in many ways I have no clue. But keep in mind that there are a lot of dialects in Chinese, that are mutually semi- or in- comprehesible. As you go back further, the likelihood that anyone you meet is speaking a dialect you don't know goes up. So it would be far more likely that someone would be able to understand someone from their home town but five hundred years ago. But I would expect you'd still see a lot of changes in the spoken language. (And five hundred years ago most writing was still using the grammatical rules of Chinese from 2,500 years ago, but that was not the spoken language. It's kind of like how latin was preserved as the language of the literati in Europe.)
Japan, Korea, and Vietnam (among others - and heck, the region and people who are counted as "chinese" has changes a lot over time) all adopted guwen as their written language at various times, and they adopted the pronunciations of the Chinese characters that were being used at the time of adoption... more or less. So a literate person from those cultures could write in a way that would be understood by other guwen readers, but their pronunciation might have diverged a fair bit from anything a Chinese person would understand. (There are some exceptions to this - you really need to know your time period well. But more or less when the countries were in direct contact with China, it's a lot more likely the elite could speak comprehensible Chinese. And then for some period afterwards. And there were more or less common pronunciations used among scholars.) Modern Korean, Japanese and Vietnamese pronunciations of classical Chinese are incomprehensible to Chinese speakers. (This I know first hand. When I was studying guwen, a number students in the class didn't speak Chinese but were studying it for their research in one of the other languages. So they tended to get annoyed that the Chinese speaking majority in the class would often use Chinese to explain things - and retaliated by doing their readings in their language of choice. It was pretty cool, really.)
no subject
So the bit about being able to read parchment that is 4000 years old is at best an exaggeration. (Do we have parchment that is 4000 years old? Last I'd heard much more than 3000 years old it's all bronze, or written on bones...)
The peroid of classical Chinese I am most familiar with is about 2,500 years old. It is a different language. The grammatical structure is totally different. There are individual characters that mean the same things, but there are also ones whose meaning has changed, not to mention a lot of characters that aren't in modern use. An educated Chinese person who hasn't made a particular study of guwen might be able to stumble through a guwen document from this period, badly - and that only because everyone gets a little guwen in school. (And I've certainly run across native Chinese speakers who don't seem to realize that writings from this period have different grammar, and they just look up the characters they don't know and produce the most appalling bad translations.)
But seriously, pretty much all my Chinese friends who I don't know from a guwen scholarship context are all "OMG, you read guwen? That's so hard!" And as I said, I rarely read stuff much older that 2,500 years.
Also, the scripts are different. I think most literate Chinese folk would be able to mostly muddle through the scripts from, say, 3000 years ago. Less sure about older than that.
Spoken language... So, we know that the pronunciation of words in the language was substantially different. My recollection is that there is a scholarly consensus that Chinese was non-tonal during that period I know best (okay, my modern is better, but of the older forms of the language) and there are a lot of reconstructions of what it did sound like - I don't know how accurate they are.
Five hundred year old chinese is a lot more modern... and in many ways I have no clue. But keep in mind that there are a lot of dialects in Chinese, that are mutually semi- or in- comprehesible. As you go back further, the likelihood that anyone you meet is speaking a dialect you don't know goes up. So it would be far more likely that someone would be able to understand someone from their home town but five hundred years ago. But I would expect you'd still see a lot of changes in the spoken language. (And five hundred years ago most writing was still using the grammatical rules of Chinese from 2,500 years ago, but that was not the spoken language. It's kind of like how latin was preserved as the language of the literati in Europe.)
Japan, Korea, and Vietnam (among others - and heck, the region and people who are counted as "chinese" has changes a lot over time) all adopted guwen as their written language at various times, and they adopted the pronunciations of the Chinese characters that were being used at the time of adoption... more or less. So a literate person from those cultures could write in a way that would be understood by other guwen readers, but their pronunciation might have diverged a fair bit from anything a Chinese person would understand. (There are some exceptions to this - you really need to know your time period well. But more or less when the countries were in direct contact with China, it's a lot more likely the elite could speak comprehensible Chinese. And then for some period afterwards. And there were more or less common pronunciations used among scholars.) Modern Korean, Japanese and Vietnamese pronunciations of classical Chinese are incomprehensible to Chinese speakers. (This I know first hand. When I was studying guwen, a number students in the class didn't speak Chinese but were studying it for their research in one of the other languages. So they tended to get annoyed that the Chinese speaking majority in the class would often use Chinese to explain things - and retaliated by doing their readings in their language of choice. It was pretty cool, really.)