Commands:

/trade - Opens the trade settings. This feature is not available in the alpha (pre-1.0).
/trade language <create/reload/edit/reset/delete> <LanguageCode> [for create: LanguageName] - Opens the trade settings. This feature is not available in the alpha (pre-1.0).
/trade <Player> - Sends a trade request to another player. They have 30 seconds to accept or decline the trade before it expires.
/trade accept <Player> - Accept a pending trade request from another player. You can also click the [ACCEPT TRADE] button in the chat to accept.
/trade decline <Player> - Decline a pending trade request from another player. You can also click the [DECLINE TRADE] button in the chat to accept. The other player will be informed you declined the trade.
/trade cancel <Player> - Cancel a pending trade request you made to another player. You can also click the [TAKE BACK] button in the chat to accept. The other player will not be informed you took back the trade.

Permissions:

trading.admin.language.create - Create new languages.
trading.admin.language.reload - Reload languages.
trading.admin.language.edit - Edit languages / see the edit UI.
trading.admin.language.reset - Reset languages.
trading.admin.language.delete - Delete existing languages.
trading.admin.language.* - All of the above.
trading.admin.reloadsettings - Reload the settings and display items for reloading settings in the /trade menu.

Custom Languages:

To create a new language, simple type in /trade language create <languageCode> <languageName> in the chat as an operator. The default English file will be created in the Languages folder inside the plugin folder. Then, you can just translate the messages yourself, save and reload the server. With the settings inventory ( /trade), just change your language to your new one.
Language Codes are always of the format xx-XX, so 2 small letters, then a dash and then 2 caps letters.
Example command: /trade language create de-DE German for the language German. Languages can later be found on my Github.


Languages:

All Languages can be found here.