why are both ImTools nuget dependency and src code included ?

[newbienewbie]

I notice that there's a nuget package reference in the Baseline.csproj <PackageReference Include="ImTools" Version="4.0.0" />

While there's also source code of ImTools copied directly in the BaselineTypeDiscovery project.

As Marten depends on both baseline and BaselineTypeDiscovery, if I manage the dependencies with paket , VS gets stuck:

The type 'VEntry<V>' in 'E:\NUGET_PACKAGES\imtools\4.0.0\contentFiles\cs\netstandard2.0\ImTools\ImTools.cs' conflicts with the imported type 'VEntry<V>' in 'Baseline, Version=4.1.0.0, Culture=neutral, PublicKeyToken=null'.