This is very much a work in progress, but I thought I should share: http://git.sccs.swarthmore.edu/web/mmcconv1/gplugin-openbsd-port/tree/
I still need to fill in the shared libs, dependencies, PLIST, etc. It builds, but I need to test whether it runs properly (which means getting Pidgin 3 working). I'm about to submit the first Lua CMake patch hunk upstream. The other two hunks seem OpenBSD-specific. GPlugin will be a dependency for Pidgin 3 when it's released.