Most of the third party tools you mention are proprietary. I’ve had constant issues with proprietary software in the past (our fields are different I guess) and so I prefer to not use them. Non proprietary software also has issues, but at least when you have issues, you know they can be fixed, either by you, or by contractors, or by the maintainers.
OK, let’s try and stay on-topic. The issue of open software (or not) is best covered elsewhere.
To the point of integrating Apple’s Cocoa documentation, it’s a relatively simple issue of work involved — it’s a very big job, and the last open source attempt was abandoned — and small target audience — serious ASObjC users with Xcode installed are only a small percentage of scripters. Dash does the job, can be integrated to a degree, is relatively cheap, and supports a whole range of languages.
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