I just tested out the forum with nginx in a subdirectory of my server (because I don't have a subdomain available right now) and I noticed this doesn't work correctly. The form target for the admin registration for is set to

/!adminrulez

for example, which results in a 404 for me (it should be

/forum/!adminrulez

for me). Support for this would be pretty easy to add I think (just add an additional config option and associated template variable) and it would be a common use case IMO. What do you think?

Well, AsmBB is designed to work in a subdomain. I have never tried to run it in a subdirectory. The path for the templates is the easiest part. Actually in order to run it in a subdirectory will need an additional prefix to be added to every URI in the engine, which might be not so easy to be done.

When I have time I will research this issue in depth.