Looks like this app doesn't even work with a 1st-gen iPod Touch... every time you try to install it you get a "not compatible with this device" error message....
Yeah this sucks and makes no sence at all!
If you run iPhone OS 3.1 beta3 the message you get on a first gen ipod is 'you need a microfone for this application'?
Common, a simple Wiki app and you need a microfone?
This is soo stupid!!! The same thing happens with Duke Nukem 3D.
Never the less you can install both apps

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Download such apps with iTunes on your Mac or PC, download the iPhone Configuration Tool from Apple (for Mac or PC), locate the apps in your iTunes library and copy them to your Desktop.
Change the .ipa extension into .zip and extract the files.
Open the unzipped folders and locate the app.
Launch the iPhone Configuration tool and install them manual to your iPod

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I installed Duke Nukem this way & I'm sure it will work with this simple Wiki app!
BTW: Duke Nukem runs just fine on a ipod first gen.
Any slowdowns on some devices will be solved after the 3.1 update will be released in a few weeks. Greets.