Ahrar al-Sham is one of the most powerful rebel groups in Syria. Together with al-Nusra, they now form the main core of the Army of Conquest which the Weste5rn media is selling as a moderate rebels. At the moment, the Army of Conquest is mostly funded by Saudi Arabia.
Many in the US are now agitating for the US to arm Ahrar al-Sham. They are said to be much more moderate than Nusra and they are not ISIS. Ahrar is not moderate at all. In fact, I think they are more radical than Al Qaeda or al-Nusra.
They have some links to Muslim Brotherhood, but ideologically they would be closer in outlook to the Taliban. Long War Journal had a good post showing their thinking and its alignment with Taliban style governance.
Of course all this is neglecting the role Al Qaeda played in its formation. Abu Khalid al Suri, a senior Al Qaeda official in Afghanistan-Pakistan, was dispatched to Syria early on and was one of the founders of Ahrar. Al Suri was killed in a ISIS suicide bombing in Feb. 2014 apparently while working on resolving the disputes between ISIS/Nusra/Ahrar.
The only thing that makes Ahrar appear more moderate than AQ or ISIS is the fact that they local and not interested in international terrorism as the other two are, ISIS in particular.