I don't think anyone believes he's not actually a US citizen. The point of conflict is that the US President is required to be a natural-born citizen. That means that if you immigrate and become a US citizen, you can become a citizen with all rights and privileges, except for one, becoming President. Like many things, the Constitution stipulates that, but doesn't really define the term in complete detail.
Natural Born is quite clear to me. You must have been born in the US. Naturally. So this would mean John Adams would qualify for President, and Alexander Hamilton would not (for sake of example ignoring the “or a citizen of the United States, at the time of adoption of this Constitution" clause). After that generation passed on, it would be impossible for anyone to immigrate to the US and then become President. I don't understand how this has become a gray area for so many lately.
If they seriously wanted Ubuntu One Music to be relevant, it was already a bad idea to require linux/Rhythmbox, but now the default player wont even support One Music without installing a plugin.
A computer scientist is someone who fixes things that aren't broken.