A contested convention is a supposedly when they candidates whose names are entered into nomination fight it out for delegates in later round voting.
A brokered convention is supposedly when party insiders work out behind closed doors who will swoop in and be the nominee.
If the party doesn't mess with rule 40, and Cruz and Trump are the only candidates who meet the threshold to be entered into nomination, then sure - - let them each make the case for crossover delegate votes in additional rounds of voting.
However, if the party makes an 11th hour change to the rules to allow only one state winners instead of eight (Rubio), or eliminate the rule altogether (Romney, Bush), then it is effectively a stolen convention.
-PJ
Trump has 6 of 8 already.