integrating vbulletin with other applications

[dionsis]

im looking to know what i will need to do to make vbulletin sync with another application

if it was something like jamroom or a custom application

do i need hooks? code a plugin?

what exactly do i need to know to make this work.

particularly stuff like login on one logins on boths, register on one registers on both and passwords are the same ( i.e. i believe vbulletin is something along the lines of md5(md5['password']) . salt

any help on these lines would be great, i like jamroom and have one or 2 custom applications and would like to know what i can do to make these work together.