[gopher] Item Type Questions

[Keiya]

So, I'm trying to write the 90% of a gopher client that can be in 'pure' 
web-usable javascript + DOM, in the hopes that there'll be a way to 
implement the other 90% in Mozilla's new extension framework soon. Over 
the course of my work, I've run into a couple questions I can't find an 
answer for:

1. Is item type 3 supposed to be interpreted as a link, or text like i?
2. What is actually the difference between 5 ('dos file') and 9 ('binary 
file')? Is it just a vague hint on what the binary might be used for?
3. Are there any item types other than i, h, and the ones in RFC1436 in 
common use I should be aware of?
4. Are CSO servers common enough that supporting them should be a 
priority? Where is the protocol specified? Is there a specified (or 
unspecified but commonly understood by clients) URL scheme for them? I'm 
already translating stuff like 8 and T into URLs, adding another would 
be easy.