Q: Will Time Capsule 802.11n work with OS X Mountain Lion

Not sure what you are trying to download.. Time Capsule is hardware.. you don't download it.

And Time Machine is built into every Mac for the last several years.

What are you trying to download exactly?

If you want to use the airport utility v5 then you cannot install it directly into mountain lion.

There are a number of methods.. here is one I used.

How to load 5.6 into ML.

1. Download 5.6 for Lion.

http://support.apple.com/kb/DL1482

Click to open the dmg but do not attempt to install the pkg.. it won't work anyway.

2. Download and install unpkg.

http://www.timdoug.com/unpkg/

You might need to allow other downloads to work, as security is tighter in ML.. go to preferences and security and set it to allow. Or control click the icon for unpkg and it will request permission to open it.

Run unpkg on the desktop.. it is very simple.. drag the AirPortUtility56.pkg file over to unpkg.. and it will create a new directory of the same name on the desktop.. drill down.. applications utilities .. there lo and behold is Airport utility 5.6 .. drag it to your main utilities directory or just run it from current location.

You cannot uninstall 6.1 so don't try.. and you cannot or should not run them both at the same time.. so just ignore the toyland version.. the plastic hammer.. and start using 5.6.. a real tool.

For screen shots see this post.

https://discussions.apple.com/thread/4668746?tstart=0