PNG is open source, which is why some people associate it with Linux. There was a bit of fluster going about with the PNG group and Apple, after an Apple patent having to do with Alpha Channels came to light-doesn't really effect the PNG format itself, just some applications that use it. So far, Apple has yet to announce any intentions with it's patent, so it may just let it be (esp. since progs like Adobe Photoshop use alpha channels, and it's doubtful Apple wants to tick off such an important developer of apps for their platform).
Konqueror is getting better, though it still has a long way to go. Mozilla is about the best way to go on a Tux box (IMHO), though Opera does fairly well, as does Galeon (Gnome's browser, based on Mozilla...)