Apple's decision to open up iOS to alternative browsers like Opera One could diversify the browser market on Apple devices, but it's uncertain how much of Safari's user base will switch to new options. The impact on Apple's stock is likely to be neutral in the short term as the overall revenue from Safari is a small part of Apple's total revenue.

Opera's announcement of Opera One, which will leverage the new opportunity created by Apple's policy change, is likely to be seen as a positive development for the company. The ability to compete on iOS devices could lead to an increase in market share and user base for Opera, potentially boosting its stock in the short term.