Developing plugin/extension based on vBulletin code

[yellowpeter]

Hi,

Recently I am developing an extension/plugin that extend some of the vBulletin functionality. I want to make sure that I am not coursing the line that violate the license agreement. Here are some of the thing I consider:

- Call some of the methods in existing vBulletin distribution, in my own php files
- Access some of the global variables in vBulletin
- and potentially... package it as add-on and distribute it to other vBulletin license owner

Can you advise if you foresee such actions are both legally acceptable and maintain good will with vBulletin development team?

Thanks...