1° I am trying to install other languages on other domain than the main domain and get this message even though my license says unlimited installations
-->How can I solve this?

Yes, you can install Komento extension on your unlimited different domain site, but you have to use full installer.

How this launcher installer work is, once you upload this launcher installer through Joomla installer page and proceed that installation, it actually download the files from our server, this is why launcher installer restricted only can install in your licensed domain.

For the download language section, only your licensed domain may be able to utilize the backend language download service. If you plan to use the language on other domain sites, you have to always copy the downloaded file from your licensed domain and apply it on the same path in other domains.

Just for your information, we'll soon remove these "domain" restrictions on our language services as we are planning to move away from Transifex.

The main reason that we had to restrict this is because Transifex is charging us quite a bit to host the language files and have it downloaded from their server. We'll look at ways on how to simplify these whole language download services.

For now, try download my attached files and replace into these following file location, in next version we will remove these domain restriction for Komento extension.

JoomlaFolder/administrator/components/com_komento/models/languages.php
JoomlaFolder/administrator/components/com_komento/tables/language.php

2° In the Easysocial forum there is an answer to this but I cannot see it because it is restricted.
-->Why do you restrict the visibility of a forum as many topics or solutions regarding one extension can be found on another forum?

You should able to access only Komento category forum post even your Komento license expired, but we restricted to access those forum post which posted in different category.

Same as documentation as well.

The language files has been installed successfully on the site.

-->Thanks a lot for the links and the detailed explanations.

I did not know Transifex would charge per download, I understand it is not very pleasant to pay for something so basic.
I hope you will find the alternative that suits you the most.

About the forum visibility sorry if I assumed that forum and documentation were no more visible after the subscription expired

Thanks for the help, have some good rest

Thanks for understanding. Well they don't really charge us per download but it equates to almost the same amount or more. You can see the monthly pricing for yourself at https://www.transifex.com/pricing/