There seems to be a lot of confusion about whether cameras are permitted or not, so let me try and explain.
There are 2 major Zip-line tour operators in Puerto Vallarta, one is run by "Vallarta Adventures" (which is the company booked by DCL); and the other is run by "Los Veranos Canopy Tour".
These are two different companies and they run their zip-line excursions in different areas of Puerto Vallarta. And to further complicate things, "Vallarta Adventures" runs two versions of their zip line tour, one is the standard "Canopy Tour" and the other is called "Outdoor Adventure".
If you go with "Vallarta Adventures" you can not bring a camera, regardless if you booked through DCL or directly with the tour operator.
However, if you go with "Los Veranos" you can bring a camera, as long as it has a neck strap. Another fact worth mentioning is that the minimum age for "Los Veranos" is 6 (compared to 8 for "Vallarta Adventures").
Here is the official website for both tour operators:
"Vallarta Adventures" (The DCL choice)
Canopy Tour - www(dot)vallarta-adventures.com/canopy-tour/index.html
Outdoor Adventure - www(dot)vallarta-adventures.com/outdoor-challange/index.html
"Los Veranos"
Canopy Tour - www(dot)canopytours-vallarta.com/info/index.html
Sorry those links aren't clickable... I don't have the post count to make link yet. PLEASE replace the (dot) with a period.