This is my personal take on things. I speak for myself, I am not a mouthpiece for ADI even though I work there and have done for quite a few years now.
The System Designer software needs to know the circuit in order to run
- that should be obvious. Some people view that as IP. ADI doesn't care, they just want to sell you parts. They would be interested if you came up with a configuration that crashed the software, or if you reported it gave bogus results, but beyond that they don't bother to look at what people submit. I'm roughly aware of the number of users as measured by EULA acceptances, and it's so large that they couldn't possibly look at everything that comes in. And to be frank, I'd hazard that most of them are pretty mundane, the product of the huge falloff in the teaching of analog circuit design skills in recent decades.
LT and ADI have different views with regards to simulation. LT puts their PC-based tools out there for people to use. I've played around with their simulator at home and it's quite good considering what I paid for it. It's certainly an improvement over other low-end SPICE-based packages, and is fine for the relatively simple signal chains that many customers want to design, but it would gag on the stuff I do at work every day.
ADI's internal simulator is the result of many critter-decades of investment, and is regarded as a significant competitive advantage. IBM, TI, ST, and the other mixed-signal biggies all have their own internal simulation capabilities, carefully guarded for the same reason. Accurate design of complex high-performance analog and mixed-signal chips requires a lot more than standard SPICE offers, and it's a lot of effort to get there - why would any of the big guys want to show their methods to a competitor?
LT has concluded that there's little competitive risk in them disclosing their simulator. ADI, TI, and others have a different opinion. Given that, the non-LT contingent are attempting to do what they can to support customers. You can like it or not, but that's the way it is despite what the conspiracy-theorists want to believe. If ADI or any other semiconductor company wants to know its competitors' tricks it's a simple enough matter to buy parts from Digikey or Mouser and reverse-engineer them; this has been going on in the industry since the beginning. As for "stealing" IP from customers, I've never seen it and doubt it would happen, the costs of getting caught would be too high and simply not worth the risk. We work *with* customers on proprietary system solutions every day, with both sides protected by appropriate non-disclosure agreements.
Use ADI's simulator, or TI's, or LT's, or one you've paid for, I don't really care. Every company offers some parts with performance unmatched by the competition, and when you need one you'll use it, regardless of who makes it or what kind of simulation support they provide. But recognize that simulation isn't just a commodity. Companies do what they can to support customers in designing in their products, but they operate in a competitive environment and need to balance what they give to customers against what they might be giving away to their competition.
I think I've said enough on this topic.
Steve