F# has been supported in Visual Studio since Visual Studio 2010, and in Visual Studio 2015 the support has improved with better syntax colorizations than Visual Studio 2010, not just IDE. This F# IDE support is officially called Visual F#.
This tooling is available as open source from Microsoft and it is available to be downloaded from GitHub at https://github.com/Microsoft/visualfsharp/.
And the F# compiler itself is open source and it is also available from GitHub (including the design proposal discussions) at https://github.com/fsharp.
The tooling is under the governance of Microsoft, but it is welcoming community contributions as it is available on GitHub. All of the community participations of tooling, ...