Jetway NF9HB Mini-ITX with 4x NIC

I would guess you can install a mini-PCIe 3G/4G modem on it and the SIM card slot is then used by the modem.
Either Free or Open should not have any problems running that board. I don't have that particular board but I have had some experience with Jetway and I would just make sure that the board doesn't run too hot. You definitely want to get a case that can dissipate heat very well.