I want to use apple's emoji font in my android application. Both ios and android market is flooded with the apps that use apple emoji glyphs in their app and I am sure none of them are licensed with apple. I want to use same emoji glyphs as well however I want to be sure there won't be any legal problem in future because of IP or un licensed design assets. Now most viable options seems to be making my own glyphs that is very similar to apple emoji fonts, however I am not sure if that would protect me legally, since it will still look like apple's original work.
Google and Apple petitioned the Unicode Consortium to include a number of these characters, ie. emoji's and version 6.0 of the Unicode Standard ended up with 722 emoji that are copyrighted. Of the other however many, most are likely licensed. That said, Apple does NOT own the right to use a smiley face or a slice of pizza, but if you are using it as a font, in the exact way Apple (or Google or the others) wrote the code to have it appear, you are infringing on the copyright.
This link is a detailed article on the topic, and also a way to sort of get around it called Phantom Open Emoji. If you specifically want to use Apples....well....Read the article.
This is a special category a bit different from other types of copyright whereby you can have similar fonts. That is what this Phantom Open Emoji allows. I checked the legal standard on the theories in this article and its right on. I would think it answers your questions.
With copyright infringement, there are always two questions: Did you copy or create a derivative work without permission, and can it be proven?
If you create a slightly altered version of Apple's Emojis, then you are creating a derivative work without permission, which is copyright infringement.
If you independently create Emoji glyphs, and they happen to look almost the same as Apple's, that is not copyright infringement. You'll notice that whether it is copyright infringement or not depends on what you have actually done.
On the other hand, you could be taken to court, and then some judge or jury would have to decide whether they believe that you copied or not. That's where a cleanroom implementation is handy (you hire designers who have never seen emojis), or at least a demonstrable history how you created the emojis. If you can only show Apple's emoji -> some slightly different emoji, that's bad for you. If you can show all the steps creating the emoji from scratch, that's a lot better.
Generally speaking, if a logo is similar enough to a trade marked logo, particularly one of the recognisability of Apple's, then you are infringing their IP. Any logo you use must be different enough that it is clearly not Apple's.