Even if we think it is always best to use an open source client, there are still circumstances when the MIT license would be a valid choice.

One of the characteristics of the MIT license is that it is compatible with most other licenses. That way, you can write a new client which combines the MIT-licensed code with code that is under some other kind of license.

Perhaps this will enable someone to write an open source client that combines parts of the existing implementation with existing GUI libraries, database frameworks, logging utilities, etc etc.

The flexibility of the MIT license is a big help if you want to encourage the adoption of niche software.