There are Mono in the repository, mono is free software but we must discourage developers to write software in C# because there is danger caused by patents held by Microsoft.
The FSF discourages developers to use it, but applications already written in Mono are OK as long as they are free. BTW, my personal opinion is that forbidding ourselves to use a bunch of free software just in case Microsoft threatens us in the future is helping them take over our freedom.
Specially since they already hold the patent for things like shutting down a computer, or doing double click.
As you said, Mono is free software. That's why it is not in http://libreplanet.org/wiki/Software_blacklist
The FSF discourages developers to use it, but applications already written in Mono are OK as long as they are free. BTW, my personal opinion is that forbidding ourselves to use a bunch of free software just in case Microsoft threatens us in the future is helping them take over our freedom.
Specially since they already hold the patent for things like shutting down a computer, or doing double click.
Closing