Back in the day, Steffan O'Sullivan demonstrated that he was pretty darn far ahead of the curve by releasing Fudge as an open game system. This was before openness was a thing, so in the absence of guidelines he just set up what seemed like very easy terms - if you want to use the system, send him two copies, and he has the right to veto use if it's really inappropriate. For hobbyists that was fantastic, but it ended up being a bit of a barrier for business. You didn't want to put money on the line when the entire system for a thing was one guy who might change his mind.
This ended up being a big deal for us after the success of Fate when we were thinking about actually putting out products. The business consensus was that sticking to Fudge would be problematic, and there's actually a copy of Fate floating around my hard drive which is a d6 based success counting system that we started drafting up in case we had to separate ourselves form Fudge. Thankfully, this problem was solved when Grey Ghost Games acquired the Fudge license from Steffan and released it under the OGL. While it was far more cumbersome than Steffan's handshake method, it was also much more reassuring to businesses, who at least kind of understood what that meant. 
Today a bit of news about the D6 System caught my attention and reminded me of this. See, the D6 system, most famously known for its use in the Star Wars RPG, has been released under OGL, sort of. The rules are open (and can be acquired as MiniSix) but not the D6 name or license, which is still in the hands of an individual. This gave me flashbacks because it feels very similar to Fudge's situation. An open system is great for the hobbyists and fans, but I'd be very leery of tying my financial fortunes to d6 for fear that I might, for example, actually call it d6 sometime, and get in a boatload of trouble.
This is kind of a shame, because I think this is an area that badly needs a strong open contender. Specifically, I mean the category of games that use recognizable dice, stat and skill lists, and have a very modular approach to rules. Examples include d6, Unisystem, Cortex and the Storyteller and Storytelling systems. It's not that I think we need another generic system - I kind of don't - but rather that particular sort of game is incredibly friendly to kit-bashing. My current experience with Cortex is doing an excellent job of illustrating how far you can tweak a system towards a specific end while keeping it recognizable. Yes, the same can be accomplished by building a system from scratch, but using a modular system as a starter kit makes ramp up easier and takes advantage of familiarity.
So, that does lead me to wonder if there's a contender for the throne out there I'm unaware of? Something more contemporary in its design than Fuzion?
1 - He only did this once, and regretted it.
2 - You do not have to argue very hard to convince me that maybe Creative Commons is a better solution, but the gaming market gets OGL and is leery of CC. That may suck, but it's a reality.
3 - That is to say, rules are added as discrete chunks on top of the system, to handle things like magic or barter. Contrast that with 4e, which uses a framework model: there's an existing chassis and new systems need to work within that framework. Or d20, which is a horrible muddle in this regard.
4 - Evidence of this can be found in the numerous ways Savage Worlds keeps seeing use. It's not truly open, but they're very transparent about what's involved in licensing the system, which is nearly as good. They have absolutely reaped the benefits of this approach.