"Support" a plugin with a an other plugin

Hey guys,

I have a question (Warning! Stupid question ^^)
How it works that 2 plugins work together.
Example: Iconomy is for InGame money. Other plugins like SimpleRegionMarket work with iconomy.
SimpleRegionMarket as example need iConomy because the player buy regions with money.
As example:
I want that a job like "trader" can use the spell "Blink" or "MagicCarpet" from the plugin "MagicSpells"

 

Well that means that this plugin has a API like bukkit API and you load it on your plugin to use some of its classes/methods, now because you can't load he classes to your plugin, you make it so in a server you install your plugin and It uses parts of another plugin, so you politely ask the server owner to have vult installed too so your plugin works.
As a example lets say you use a method of vault like .geteconomy, then if vault is not installed in the server your plugin is installed on, it can't access the method and it doesn't work.

Reply if u need any further help.

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

If the license is right and you have the source, you can change the source to what you want for you're server. But if you don't want that you can also add the plugin as an library