first, excuse my bad english and you are doing a great job!
my suggestion is 'Microsoft Visual Studio Code' (vscode).
and the sourcecode is hostet on github: (MIT License - here you can also see a screenshot)
it is possible to build a portable application:
MS writes, that vscode free for private and commercial use:
Why this editor?
vscode can be extended with many free modules e.g. for ssh connections, python, markdown and so on.