erm…cough cough…
umm, how about
I think you will find it supports the required Operating systems and
is open source, and is SOOOOOOO FileZilla like, its shocking.
it might be a clone, or you never know, even,
Gulp
the real deal!
And I have never had an issue with it.
Humour (and bemusement as to WHY NOT FileZilla?) aside,. I have also used cyber duck
you can get the source code on GitHub for them I think -but, alas, no Linux support