I thought you came here to troll at first...but then I realized you had a real question.
The only specifics I know about this is from what James of FiiO has told us on this site. I'm not a product creator or anything so I wouldn't know but I have yet to hear anyone say otherwise.
But Apple has this MiFi program
You know those 'real' devices you see by Belkin, Bower and Wilkins that has the logo that tells you its legit and what not? Those are there for a purpose. For the most part, because the 40 pin dock is Apple's own proprietary setup, they can choose what to do with it. So these 'lisences' allow them to make the dock
Most things are VERY simple so fakes come out easilly. Any fake dock is just a matter of copying it.
However for our case, it won't be easy because one needs to bypass the DAC. From what I've heard, there is a special 'code' needed that you have to get from Apple which allows access to the actual internals of the iPod to allow you to bypass it.
This is a big reason for why the only devices that can bypass Apple DAC are $500+ dollars. Because it cost them a lot of money and time and effort to get the program lisencing from Apple.
How do I know this part is true? I don't. But think about it this way. Audiophilia is HUGE in China. If there is no other product from China that can bypass an Apple devices DAC at the cost of $20 or something(if it was really that simple right?) then we can be pretty sure that this 'code' and everything about how one can go to access an iPod/iPhone's DAC is hella hard. Because if China audiophiles haven't done it in a decade for cheap cheap cost. Then what I've heard is probably true
One way people bypassed this constraint was through the 40 pin dock iPad variants and using the Camera Connection Kit. Because you see(lightbulb in brain lights up), if one can't get a device to bypass the DAC made by an external company. Why not use Apple's own CCK adapter to be the one that DOES the bypassing first!(ding ding ding)
So yes, iPad(with 40 pin dock) users with CCK can use an external DAC of their choice as the CCK(only real Apple versions) does the heavy lifting for them. And boom. Most users have to use a DAC that has low power draw though as the CCK has a limitation. BUT another user in this thread was able to use another small hack to make it so that you can use any DAC you want regardless of power draw through some nifty engineering and understanding of how USB hosts and all that jumbo works.
Why type all this? I have a mechanical keyboard, and I love to hear the sound and feel of me typing long stuff. It feels absolutely boss, and it helps keep me sharp and what not. My gosh its so tactile and amazing. Every single time I type. Just say8ing