This is in response to my Hollowpoint Reveiw from 2011; I'm presently playing clean-up on some draft blog posts.
Fiasco, Hollowpoint, Do: Pilgrims of the Flying Temple are each rules-lite games that could be summarized in about 2 full pages; Hollowpoint is by far the most rules intensive of these three.
Disclaimer: I am not a game publisher nor designer, so I don't have any skin in the RPG business.
Pros to Releasing the Rules
Distill the fluff from the crunch: What are the core rules and what is the product's identity. I know I prefer to have the lovingly crafted book, with a well thought out layout vs. a webpage with presentation as an all to often after thought.
Easy for third party adaption: If someone wants to expand on the game, providing a clear path makes it easier; Yes they could just ask the publisher for permission.
Product Preview: By giving access to the rules, crunch-minded people can “test drive before buying.” If you have a highly stylized presentation, providing just the rules might be detrimental to your game (I'm looking at you my most gorgeous Do: Pilgrims of the Flying Temple).
Cons to Releasing the Rules
The skeleton of your game is now free to the public. Will it hurt the sales?
What other consequences are there?
What license do you release under? OGL? Creative Commons 3? GPL? MIT? Apache?
Reality of Releasing the Rules
According to US copyright laws, the language used to describe a rule is copyrightable, but the underlying concept of the rule is not. So if you can, in your own words, describe a rule, then you are likely not infringing on the copyright holder.
If I had the inclination, I could rewrite the rules of a game and release them. It would then be a matter of whether the copyright holder of my source material decided to pursue a copyright infringement case or not.
This reinterpretation would be rather dick-ish and is in direct violation of Wheaton's law. Besides, would I rather copy someone else's work, or would I rather work out my own creation.