The article goes into specific details about how new technologies would be needed to overcome many issues.
For example, Mars One plans to obtain all food from locally grown crops. The vegetation would produce unsafe levels of oxygen. This would set off a series of events that would lead human inhabitants to suffocate.
To avoid this dangerous situation from happening, a system to remove excess oxygen would need to be implemented. This technology has not yet been developed for use in space.
In order to not die from thirst, Mars One plans to obtain all it's water from Martian soil, by melting the ice contained in it. But technology to bake water out of soil is not yet ready for deployment on earth let alone in space.
Studies like this make it clear that Mars One will not be feasible. This is why we need a consortium of nations to back a Global Space Agency where we send not a handful, but a million people to colonize the red planet.