Someone in the comments of an earlier post asked the question about why anyone would ever play a retro-clone. This is a topic that, if you follow message boards, has been hashed to death; perhaps not so much in the blogosphere.
So I'd like to clarify some of the design objectives of OSRIC and of Swords & Wizardry. These are the only clones where I was privy to the design objectives, so I can't speak for the others, but I suspect that their design objectives are similar (although each clone faces a different context, which will be clear when I point out differences that exist even between OSRIC and Swords & Wizardry).
In terms of OSRIC, since it was the first clone ... wait, let me interject something. There is a historical progression toward OSRIC -- Hackmaster was a retro-game under a license, and then Castles & Crusades was a retro-game using the OGL. Without those steps, OSRIC would probably not have been conceived. I call OSRIC the first clone because it was the first rulebook to use the "rules aren't copyrightable" aspect of copyright law in addition to the OGL. It's a fairly fine distinction, but I do think that it's relevant for various reasons that I won't go into because it would turn this post into a dissertation.
Back to the topic. Let's start with OSRIC.
Since OSRIC was the first clone, we made an incorrect assumption. I had started the original draft with the assumption that it would be played, but as the draft progressed it became clearer and clearer that what we were creating was simply a tool for publishers to use a "shared brand name" that would indicate compatibility with 1e, and bring the publishers into the legal safe harbor offered by the OGL. As it turned out, we were wrong about that. Many people use the book at the gaming table, for various reasons that Stuart and I didn't really consider early on. Since there wasn't another example of a clone out there, we had some blind spots where we simply didn't predict certain benefits of the book.
So, the only operative design considerations with OSRIC were to stay true to the original material and to provide a legal safe harbor for publishers. Gamers didn't even enter the equation. Simply as a matter of doing the job in a workmanlike fashion, we made sure that the material was well organized. And simply from the standpoint of making it easy for publishers to get a copy, we distributed a pdf for free. Simply because they weren't our rules, we didn't charge any profit on the printed copy. But the combination of all those elements happened to create something that was used in ways we didn't foresee.
Things we didn't Foresee:
1) Because the pdf was free, and available online, people who were trying out 1e for the first time, and people who were teaching new players in an online game, often used OSRIC because it was available to download instantly and free. You didn't have to tell players to go to ebay or Amazon - just download this thing, here.
2) Because we had organized the material in a more "modern" fashion, it was more intuitive for people who had only been introduced to RPGs after 1e. Thus, as in #1, it was often used as a teaching tool. "Read this free download, and then we're going to play with the original rules, which work the same way."
3) What I call the "living game factor." Many people want the community of a game as well as just the rules. They want to play a game that is in print, that has modules and supplements coming out. This attracted several people to OSRIC not as a reference tool, not as a teaching tool, and not as a free starter kit. It attracted them to the idea of playing the OSRIC rules using the OSRIC book. This was, for OSRIC, probably the least foreseen of all the unforeseen things. I understand it in retrospect, but Stuart and I didn't predict it at all. It was a complete surprise.
This might not be so clear if you're looking at OSRIC 2.0, which was revised based on requests. But if you look at the old OSRIC 1.0, it's pretty clear: no monsters, because people would be referencing the original book. No information about hirelings or any of the finer points, because a publisher doesn't need that as a basis for writing a module. We expected maybe 50-75 unique downloads from people who wanted to publish a free or for-profit module. When the number hit 50,000 unique downloads in the first month, we realized that we had overlooked something in our predictions.
Swords & Wizardry
Moving on to Swords & Wizardry.
When I did Swords & Wizardry, I had some different design objectives than OSRIC for two reasons. First, simply the context of the cloned game: (a) the original game books are really expensive compared to 1e, (b) by this time, WotC had pulled their pdfs off the market, so there were no legal "official" electronic copies of the original books, (c) the 0e books are generally considered to be less organized or harder to follow than the 1e books, and (d) the original books had never been compiled by topic matter - the later parts of the rules were all in supplemental form. Secondly, when doing Swords & Wizardry, I had the experience of seeing how OSRIC had been used (and also the experience of seeing how Dan Proctor had handled Labyrinth Lord to meet gamer needs that we hadn't predicted with OSRIC).
So, with Swords & Wizardry, I used a different set of principles.
1) As with OSRIC, create a legal safe harbor for publishers - nothing new here.
2) Unlike OSRIC, make the assumption that the book will be used at a gaming table or as the rules for a "teaching game." This was much more important for S&W because the original books were far less available and much more expensive than for 1e. This altered the writing style somewhat, and it also mandated that the book include such things as monster descriptions.
3) Unlike OSRIC, create a centralized community location, which I did by setting up a message board at http://swordsandwizardry.com/forum/. This took into account the "living game factor."
4) Unlike OSRIC, create a dedicated website; again, this is to take into account the Living Game Factor.
5) Because I could predict, after OSRIC, that Swords & Wizardry would end up being used as a table game or a teaching game, and because the original books contained huge quantities of alternative rules (some of them at a very fundamental level, like sequence of combat and attack rolls), the organization of Swords & Wizardry follows a VERY different tack than in the original rules. I began with the way a "Basic Book" works - a clear little pathway of clear "default for S&W" rules, that introduce the skeleton concept. Then I tried to weave that into the real way that 0e works ... there are virtually no "official" rules to oe at all - even combat is a matter of house-ruling. Thus, S&W approaches the original game in a two-step process; an easy introductory pathway of defaults, surrounded by reminders that once you've "got it," it's time to tailor and innovate it for your group. That's what 0e is -- a framework for innovation -- but in consequence the initial simple pathway is very hard to find in the original books, even for many AD&D players, much less someone who started with 3e.
The retro-clones simply weren't designed or intended to actually compete with the original, underlying rules. We didn't even conceive of that possibility with OSRIC 1.0. And with Swords & Wizardry my main focus was to provide that one-two punch of (a) organization + pathway of clear rules for the introduction, then (b) innovation, choices, tweaking, and personalization once the basic concepts are in place. It's a gateway tool. Although being realistic about it, I knew from the example of OSRIC that many people would end up sticking with the S&W rules - and even more so than happened with OSRIC because the original books were far more expensive than the 1e books.
In other words, my main objective was to introduce the fundamental concepts of 0e, which are not intuitive to most later-generation gamers, with the expectation that those who can afford the original rulebooks should and will seek them out. When the new gamer reads them, they won't create the -- very common -- perception that they are so vague as to be unusable. Having already seen them in a more organized, compiled format, the newer gamer can assimilate the original books much more easily. It may be difficult to understand why this was a needed approach for spreading the 0e approach into the mainstream - but I can tell you that on ENworld and other mainstream sites I have seen over and over and over the following types of reactions to 0e: "It's nothing more than an incomplete version of 3e - you have to fill it in with 3e rules all the time," or, "It's so disorganized I can't see why anyone would bother playing it," or "it doesn't even contain rules for combat, it tells you to look at this 'Chainmail' book." Whether or not the grognards agree with the validity of these reactions, these are real and common objections that must be answered in order to bring 0e-type gaming back into the mainstream. They are existing memes, thought viruses, and they are the reaction of most newer gamers who read those original books.
Getting 0e type rules into the mainstream is a matter of pragmatism. It can't be done with wishful thinking that WotC will reprint 0e, and it can't be done by protesting that "anyone should be able to figure out those books." WotC won't, in the former case, and new gamers don't care to expend the effort, in the second case.
My hope is that anyone with the money to buy original books will do so, and that S&W will have served as enough of an introduction to allow a newer reader NOT to have the common negative reactions; but, instead, to assimilate and use the original books. And for those who can't afford the original books, S&W is only then intended as the end-product table-book. In this economy, that's unfortunately applicable to a lot of people.
And so, my hope is that the retro-clone rules will serve as a jumping-off point, a teaching tool, a convenient way of telling people "you can download it today from right here," and an inexpensive book for when you can't afford the originals. If you prefer the community of the retro-clone circles, or if you like the energy of a published game, that's all to the good. But whether you use them for flavor, inspiration, reference, additional material, or as the table rulebooks ... the original books are really where it's at.
I will be realistic - the current prices on the 0e books have risen so high that I think S&W is going to end up being a significant part of 0e play as time goes on. It's simply a matter of scarcity. But I would infinitely prefer that Swords & Wizardry be used - ultimately - as a tool and a gateway for people to access and appreciate the original game in all its quirky, wondrous glory.
...but WotC ain't going to reprint the originals, so we have to deal with that fact as pragmatically as possible. Retro-clones are one avenue of response.