You said in the readme:
OmniSharp-Roslyn is built with the .NET Core SDK on Windows and Mono on OSX/Linux. It targets the net461 target framework. OmniSharp requires mono (>=5.2.0) if it is run on a platform other than Windows.
So the question is that why we don't use .NET Core for OSX/Linux platform? I think it's cloud be better and we'll have .NET Core advantages instead mono. I there any plan for this?
Also here we have an image that shows even OmniSharp for Windows is .net framework.

This is by design, and is needed to in order to use MSBuild tasks targeting Full Framework - as they don't work on CoreCLR. Note that OmniSharp ships with its own embedded mono runtime too, so it can run even if you don't have a global mono installed. In other words, a full framework based OmniSharp can support all kinds of projects (full framework, .net core, unity etc) but a .net core based OmniSharp has a lot of troubles supporting non-.NET Core projects. We used to build .NET Core OmniSharp in the past but we went away from it.
You can find more information here https://github.com/OmniSharp/omnisharp-roslyn/pull/988 and here https://github.com/OmniSharp/omnisharp-roslyn/issues/666 and here https://github.com/OmniSharp/omnisharp-roslyn/pull/915
Thanks!
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This is by design, and is needed to in order to use MSBuild tasks targeting Full Framework - as they don't work on CoreCLR. Note that OmniSharp ships with its own embedded mono runtime too, so it can run even if you don't have a global mono installed. In other words, a full framework based OmniSharp can support all kinds of projects (full framework, .net core, unity etc) but a .net core based OmniSharp has a lot of troubles supporting non-.NET Core projects. We used to build .NET Core OmniSharp in the past but we went away from it.
You can find more information here https://github.com/OmniSharp/omnisharp-roslyn/pull/988 and here https://github.com/OmniSharp/omnisharp-roslyn/issues/666 and here https://github.com/OmniSharp/omnisharp-roslyn/pull/915