Darvond: I thought Daum was moribund?
Why not give Staging a try? Normally the latest DOSBox releases, DOSBox Staging among them, are indeed the better choice. Unless you need a feature that the newer ones don't have.
In this case the author that wrote the De-interlacing Shader wrote it for Direct3D in the .fx format that Daum supports.
Most current DOSBox compilations use OpenGL Shaders in the .glsl format.
As I mentioned earlier in the thread, it would be interesting if someone would be able to port this Shader over to the .glsl standard. As I don't know if anything equivalent is available at this time?