1) What proprietary firmware? I've not seen any that affects mainstream app developers. I've only seen such that adds value to a particular device. E.g. Samsung adding their cool settings shortcuts to the notification shade.
2) Android, while open for any use, has standards to meet if you wish to use its name. To say your device is a certain version of Android, then it MUST run a standard set of APIs for that version.
3) In real life (not in forums), Android (and iOS) fragmentation is not a major problem. Heck, Rovio -- author of Angry Birds --just came forward to note that anyone claiming it is (such as Jobs) is just making a mountain out of a molehill.
4)Can you clarify what this means? Thanks.
1) It is on it's way.
2) The developer will need to write unique API's for each device manufacturer's Android. Samsung, Motorola, HTC, LG will all move to lock down their devices MUCH more aggressively than Apple has, or will. Due to Apple's MUCH stricter control of API development. Android will always be a larger market share, less satisfactory in the implementation, and end user experience.
3) Rovio also states that a developer can't make money on the Android Market due to the App Store, and Android Fragmentation. For Pete's sake Rovio has to give Angry Birds away as an Ad App. Giving you the option to pay for a download to remove the advertising.
4) See #2.