Wouldn't it be nice to have a free commute? If you take on the responsibility of driving for a vanpool, the passengers in your van will pay for your share of the monthly costs. In addition, you'll get free use of the van during off-hours and on weekends.
As the driver, you'll be in charge of the van. That means you'll be responsible for taking the van in for scheduled (or unscheduled) maintenance appointments, keeping usage logs, and making sure the van is clean, full of gas and well-maintained.