I think you should check the small print for their precise definitions of "no processing". All images are processed - even "straight out of the camera" images are processed by the camera - so the question is really about what's allowed and what isn't.
I would suggest that *global* changes to exposure, contrast, saturation, white balance, sharpening, etc. should normally be acceptable, but *localized* changes (which might include gradients, cloning, vignetting, etc. as well as the kinds of things you can do globally) wouldn't be acceptable.
And Lightroom is an excellent tool for making global changes of this nature.