All modern, competent browsers should support all of the features. However, as usual, use IE at your own risk. It looks like IE 10+ and Safari 6+ should support all the features. Firefox and Chrome should work with all features back to versions 3 and 4. Opera 11 and up should be fine. If you really need to use Papa in old IE or Opera, then keep the fancy features off and you may be in luck.
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<h4>Is it open source? (Can I contribute something?)</h4>