Apple (NSDQ: AAPL) will allow third-party apps on the iPhone, the company officially announced today, after rumors and hopes to this effect for a while. Of course, this is a turnaround from Jobs and Apple on their desire to control the environment, but with rampant hacking of the phone since it launched, this was the only logical way to go. Also, anecdotally, the iPhone sales may need to be kickstarted after the initial buzz, so this might have helped changed the company’s mind as well.

Jobs said in a letter that the company intends to release a software development kit in Feb that will let people outside the company to create iPhone and iPod touch apps…on why it will take so long: “It will take until February to release an SDK because we’re trying to do two diametrically opposed things at once—provide an advanced and open platform to developers while at the same time protect iPhone users from viruses, malware, privacy attacks, etc. This is no easy task. Some claim that viruses and malware are not a problem on mobile phones—this is simply not true.”

And this small acknowledgment of Nokia (NYSE: NOK) is amusing, to say the least: “Some companies are already taking action. Nokia, for example, is not allowing any applications to be loaded onto some of their newest phones unless they have a digital signature that can be traced back to a known developer. While this makes such a phone less than “totally open,” we believe it is a step in the right direction. We are working on an advanced system which will offer developers broad access to natively program the iPhone’s amazing software platform while at the same time protecting users from malicious programs.”