You can put KOReader on your Nook! And you don't even need to root it in order to do that.

Here's some instructions on the process:
https://www.mobileread.com/forums/sh...&postcount=349
I think the only extra thing to note is that they added one extra thing that you'd need to do around step 2. In order to enable USB Debugging, I think there's now a password that you have to put in. I enabled it before they added the password, but from other posts, it sounds like that password is just the model name of your device (NOOK-BNRV1100 for the GL4).
I'm not sure how to disable the touchscreen entirely, but I did see a setting in KOReader on my GL4e where I could uncheck two boxes to disable page turns by swipes and/or taps. That essentially locks page turning down to the physical buttons, but the touchscreen is still active for any menus/gestures.