Okay, if you're getting apps from the GetJar market, the first thing I'll have to tell you is that you need to go into Settings - Applications and then check 'Install Non-Market Applications'. The way the Kobo's set up by default, it won't install anything except through the official Google App Market, which is not installed. Therefore, if you want to install applications downloaded from GetJar (the Get Apps link), you need to tell Android that you're allowing it to install these applications.
Beyond that, these prompts are telling you what an application does BEFORE you continue with it, unlike Windows or MacOS where you could install a program that basically gives your computer away to someone in Estonia as Windows won't tell you the program you're installing takes all control away from you.
In the case of Overdrive, it needs to know what hardware it's on, it needs to be able to save files or delete files onto the device, and needs Internet access to connect to Overdrive's servers - which is why it's asking for permission to access information on the device, to read and delete items off the SD card, and to get Internet access. It's telling you ahead of time what it needs, which is meant to give you warning if you're installing something that's not legitimate (for example, a 'free' wallpaper application which needs access to all your Contacts, needs to be able to connect to the Internet and send SMS messages is probably not a legitimate program).