So here's in defence of plain old normal non-reusable Django apps. The ones that probably power most of your current awesome Django sites. They rock. Easy to write and build out a site with. Django apps deserve credit for being so rapid to develop and having a very small set of boilerplate and required code (just a models).
So before people come up with schemes for making apps reusable, please remember, we've got a great solution for building apps now. Let's not ruin the speed and simplicity of Django app whilst in pursuit of improved reuse.