Larry Hryb, aka Major Nelson, has confirmed that Windows 10 users on PCs and mobile devices will not be required to have an Xbox Live Gold membership to play online.
In an effort to create a single unified Windows 10 ecosystem across multiple devices, Microsoft is working on integrating the Xbox platform into the system. The integration will bring benefits such as cross-buy, cross-play, gameplay streaming between the Xbox One and other Windows 10 devices, and much more. However, some users have expressed concerns whether they would have to pay for the service to be able to play online. After all, PC users aren't used to the idea of paid access to online features in a game.
Fortunately, Microsoft quickly allayed those fears. Answering to a concerned fan's question on Twitter, Major Nelson made the following statement:
@haydencd Not charging. Xbox Live Gold will not be required for online multiplayer gaming using our service on Windows 10 PCs and Phones— Larry Hryb (@majornelson) march 5, 2015
Source: Major Nelson via Twitter