I'm not familar with Mike Fort's LToBPF. It looks similar to LToUDP in that it shovels raw LLAP frames over an Ethernet network.
The AppleTalk support in GSport/GSplus is much more substantial. It is a true LLAP-to-ELAP bridge. That is the emulated IIgs acts like an EtherTalk Phase 2 client on the network. It takes LLAP packets coming out of the emulated SCC, strips them to just the frame data, applies ELAP headers, and then ships them out via a libpcap interface. It also has a AARP service that ties into the LocalTalk discovery on the emulated IIgs.