To answer most common questions: (I may be wrong, I'm just another guy)

Do I need NITdroid?
Nope. But you may need Bİonic libraries, download them from thp.io and place them on the same folder you placed apkenv.

"Permission denied" message
Run this: "chmod +x apkenv", then ./apkenv, It should work now.

Here's a quick wiki page: http://wiki.maemo.org/Apkenv