As stated in our website:
SlingPlayer Mobile for iPad requires iOS 4.2 or later. If your iPad is running an earlier version of the iOS, the application will not show up in the App Store for you.To get the app, you need to update your iPad first. Just connect the iPad to your computer and update the iPad software in iTunes.
Regarding the second part of your comment, these charges are applied because the platform is different for every one of these devices. The following link will provide you with further information about this situation.
Almost every company does this in regards to iOS updates. There are several older versions of software apps that simply don't run or have bug problems after upgrading the OS until you update to the new released version.
In the same manner, some apps functionality (or sometimes the app in it's entirety) is created for a specific version of the iOS since they were using the developers verison of that particular release in order to test functionality and actually write the coding.
This is simply common practice and I can garentee you this will NOT change on any platform nor from any software vendor including Sling Media. It is simply absurd to have to make a multitude of variations due to someone being out of date. It's not like you can not use the version you possess now; however you won't ghain the functionality of the new version until you do update to 4.2+.
I'd be more flustered over apple taking the orientation lock out then what your complaining about to sling.
BTW, evemn on 4.2.1, you can jailbreak and add the orientation lock functionality back though cydia.