The promise of Portable Class Libraries for the .NET Framework has been limited up until this point due to its bias towards Microsoft-based stack. This bias was expressed in the form of a software license agreement that legally restricted PCLs exclusively to various Microsoft platforms including Windows Phone, Xbox 360, and Windows desktop. Previously if you were a developer seeking to build a multiplatform application that would work on non-Microsoft platforms via Mono as well as a Windows-based one, the license prevented this. This artificial restriction limited adoption of PCLs, but a new announcement from Microsoft eliminates this often frustrating legal restrictions, providing a new reason for developers to consider using this technology.
As Microsoft Program Manager Rich Lander states, now Portable Library Reference Assemblies can be used on any platform. Xamarin’s Miguel de Icaza commented that this release is “great news” and that it will enable developers “that want to create binary assemblies on platforms that do not have Visual Studio installed (Mac, Linux or even Windows without VS installed)”.
This release is a great step forward, but work does remain as some other Microsoft PCLs remain restricted. A popular UserVoice request remains outstanding, and as a result this means Microsoft produced libraries (including Immutable Collections) remain restricted. That said, this is a move in the right direction towards openness and increasing developer support.