Aaron Edwards

Tired of your custom plugin and theme translation files getting wiped out every time you use the WordPress auto-updater? Install and activate this plugin and 
WordPress will look for missing translation files in the WP_LANG_DIR where you keep your WordPress translation files.
<h4>UPDATE</h4>
In WordPress 3.8 and greater this plugin’s functionality is included in core. You can put translation files in: 
* Plugins: /wp-content/languages/plugins/textdomain-locale.mo 
* Themes: /wp-content/languages/themes/textdomain-locale.mo
A free plugin by Aaron Edwards of <a href="http://uglyrobot.com/" rel="nofollow ugc">UglyRobot Web Development</a>.

Translation Preserver

A simple plugin that helps preserve your custom plugin translations through auto-updates by allowing you to put them in your WP languages folder.

weDevs

Sabbir Ahmed

alamgircsebd

Rafsun Chowdhury

Dokan, Inc.

Dokan Multivendor is based on the famous eCommerce solution WooCommerce. To enable multiple language feature WPML is the most reliable solution. These 5 extensions below is required to translate a WooCommerce store-
<ol>
<li><a href="https://wpml.org/?aid=106335&affiliate_key=EbXH25fvBE9b" rel="nofollow ugc">Sitepress Multilingual</a></li>
<li>WooCommerce Multilingual</li>
<li>WPML Translation Management</li>
<li>WPML Media</li>
<li>WPML String Translation</li>
</ol>
You can purchase and download all these plugin from the same site. Some of these are free!
After purchasing all these extensions and installing, you need to install this extension. It will not work unless you have activated all the plugins mentioned above.
Please remember to set the URL structure to <code>site.com/lang</code>.
Dokan does not support URL parameters. So you can NOT set the URL structure to be <code>site.com?lang=nl</code>
This extension does not have any settings. Everything is controlled from WPML settings page.

Dokan WPML

WPML integration for Dokan Multivendor Plugin

Translation Preserver vs Dokan WPML