The fact that it's linear is significant in it being simple to use :P But yeah, you really don't need to know how to program to use Ren'Py. You need to know some very basic Python for nonlinear VNs, but it's almost nothing as far as knowledge; the difficulty is in planning out the paths and which variables you need where and when, because you could end up needing to either completely rework older code, or repeat the same lines of code over and over again.