After interest has been shown, I recompiled the dwgCrawler so that it will work for AutoCAD2009 and also AutoCAD2012, 64bit. They are available at ncadaddons.tumpliner.com.
I checked into further versions of AutoCAD and decided not to go that route because I am essentially a 2D user of AutoCAD, and I can see no further value for 2D use in later revisions beyond 2012. Also, the API changed after 2012. Changing the API, so that programs compiled for earlier revisions will need to be recompiled, gets a little annoying, especially when there is no real value gained for 2D work. So that is another thing I like about NanoCAD. I compiled it once, and I do not have to recompile it each year or every other year. They are not coming out with changes to the API, and I think they value the customization programmers enough that they will not break the API to require recompilation for little or no reason. They do not have the motivation to get people to upgrade every year-- they are not charging for the software. They only take a cut from the action if a developer is selling an add-on for use with NanoCAD.

Actually, NanoCAD exposes the same API that AutoCAD does for use with VB.NET or C#.NET, so it must be able to understand the dwg database architecture just fine. Also, I have used it for years, importing and exporting to dwg. I have never had a problem opening any of those files with AutoCAD, or any AutoCAD dwg with NanoCAD. I don't think any other clone can say that. There is nothing fake about it.
I have never heard of AutoCAD Content Center. Are you referring to the one used with Inventor? I would not know anything about that. I have only used AutoCAD and NanoCAD for 2D work. This is not aimed at 3D work.
Speaking of not understanding the structure of AutoCAD's database-- I doubt if Windows does a great job of that. Will it find text embedded in block refs, attribute text, mtext and regular text? I doubt it. I have seen several comments of it not working fully. I have not seen any comment that it does work fully. I think I read somewhere that it does not pick up everything in formats after 2010.
You know, it sounds like you have some other prejudice against NanoCAD, and I am curious what that may be.

Now I get the impression you are just here to push nanoCAD.

Windows search indexing is enabled when the program is installed.  Most users don't know about it and even if they did many wouldn't even know how to disable the feature unless they went looking for a solution online (ex. - Microsoft or PCWorld website).

John Connor,
     thanks for the reply. I did check the link you posted. I did not realize that AutoCAD has this capability. Do you know if it works? If I remember right, I tried a Microsoft Search tool a few years ago that was supposed to find text within a drawing. I could not get it to work. That was about 3 or 4 years ago. I might have been using AutoCAD2009 then.

I'm not sure you'll find any nanoCAD users active in this forum.