Ah, I see. Interesting ideas. I'll throw out some thoughts since you asked for them - just random musings.
http://www.symbols.com/
This has been my source of ideograms in the past. Not sure if it'll help you, but it's interesting anyway!
-Ergonomic
I'm thinking ergo=work. A hand? The yin-yang is pretty, but it may be lost on many. As an alternative interpretation, the wave you made may also look like flowing water which again could work well with the concept of ergonomy.
-Easy
You're onto something. Obviously, it has to be a simple design. An arrow forward ("just go for it")? Simply a dot in the middle of the circle?
-Fast
This and the cross were the ones I intuitively understood from just looking at your designs. Maybe one less "turbine blade" for clarity?
-Multilingual
Should not use a hamburger - they're bad for you! ;) I think it looks good, but please also tell us about your other idea. I'm thinking about whether any simple icon says "language" but can't come up with anything other than a Chinese word character which is silly (and Colemak doesn't work with Chinese!).
-Free
Tricky. I'd use a crossed-out dollar sign because everyone in the world must be familiar with the $=money thing. Just think about the eyeballs of cartoon characters turning into dollar signs for instance. The ¤ symbol actually means "currency" but I think many people don't know that although it sits around on a lot of keyboards. The Ubuntu logo wasn't familiar to me, and at any rate I think it becomes too complex for an effective ideogram.
-Cross-platform
Good one. The diagonal cross may seem negative ("crossed out"), so I'd consider using the "sun cross" instead. It's been a while since anyone used that for anything bad and were listened to, so I'd think it's safe to use now. And at any rate, such a simple symbol must be available for all. And the Sun is nice. :)