- Implies an affiliation with the humble bundles, but has none
- All of the software is from the same developer
- The options for where to send the money are 1. the developers, 2. a non-profit organization run by the developers, or 3. the bundle website, also run by the developers
- The software looks really terrible
- If it's GPL, where is the link for the free distribution of the source code?

Grado SR-60s are the way to go for your requirements. They are, hands down, the best headphones available under $100. The only drawback is that they are open stage, so you can hear sounds around you, which is not so good for a metro or bus ride. But it sounds like that's an advantage rather than a drawback in your case. SR-60s will run you about $80 USD shipped. Oh, and don't succumb to the temptation to get the SR-80s just because they've got a higher model number. The 60s are far better for non-amp-driven listening.