A customized version of etoViewport, forked primarily to support a customized version of OpenTK.
Additionally, you'll find a build system implemented in Nuke. To build, just clone the repository and run the Nuke build script: with the Nuke global tool installed, simply open a command prompt and run nuke in the root directory. Without it, open a PowerShell or Bash terminal as appropriate for your OS and run .\build.ps1 or ./build.sh, respectively.
Running the build at least once will ensure OpenTK is built; with its assemblies available to serve as references, the project can be edited and built from within an IDE.
Test projects can be built by appending --BuildTests to your build command. OpenTK will be rebuilt if you append --RebuildDependencies, or if lib/opentk/bin/OpenTK/OpenTK.dll is missing.