Probably a socialist, but he does take some libertarian positions.
Also some "non-socialist" positions hard to peg solely as libertarian or conservative. From a review of "When You Ride With Bin Laden You Ride Alone" at Amazon.com:
One of my major beefs is that Maher seems to believe that we are at war with Islam -- all of Islam. Such views are not helpful. They only make matters worse by putting everyone in the same category. If we judged Christians as being all like Jerry Falwell no one who believed in Christ would look good either.
Maher's support of profiling Arabs also doesn't make sense. There are tons of scenerios in which an old lady, a child, or a love struck 20 something could accidentally bring a bomb on board a plane. It's not about knowledge or intent, it's about manipulation. I want the old ladies frisked, including my mother! Why? Because some people are too trusting and just might make a mistake.
There are other views expressed or, unfortunately, outright ignored. In one poster he highlights the stoning of Muslim women while at the same time ignoring the rape and brutualities towards women here in the US. In another essay he demands more funding for the Pentagon, the agency that gets more than 50 percent of the discretionary budget and was judged by the GAO as being the most mismanaged federal agency in the entire US government. Please! In another poster & essay he supports the reporting of suspicious activities to the government. On its face, that might make sense. But then remember how many idiots there are out there and how many people have an axe to grind with someone else.
The good posters and essays, on the other hand, hit dead center. The "why they hate" us posters are great as is Maher's support for better pay and respect for firefighters, soldiers and police officers. The pages focusing on our over consumption of oil are perhaps the best, most notably the one on the front cover.