My reading of it is that they appear to be saying that freelan does transparent NAT traversal, whereas OpenVPN would require explicit port-forwarding.
--
I just happen to be here doing my first OpenVPN implementation this last few days.
It appears that FreeLAN is all about transparent bridging VPN, rather than routing VPN. Thus, the "LAN" part of the FreeLAN product name is particular apt.
It is noteworthy that the words "Ethernet" and "bridging" are absent from the product FAQ. This is most unfortunate.