Strange, I just tried it on a test site and works as intended.

can it be configured to work on specific forums ?

Too me I have the same important problem like lettebasse.
Is it possible to add this very important feature?
Thanks in advance.

As the developer has not been on in three years, and the mod has not been updated in five years, I doubt it will ever get updated at all.

Thanks Ozzy.
Do you know what mod do the things we ask?

Any answer?

Actually looking at the code, it seems like you can do it on a per forum basis, you just need to set it in each forum individually.

Sorry but how to do this?

Sure that is really incredible that on Vb.org there isn't a mod like this..
Is also a simple mod.

Try editing each forum, ACP --> Forums & Moderators --> Forum Manager then edit each forum and look for this setting, Exclude this forum from hiding links from guests, it is set to hide by default.