I been looking for this option a while now. I there any way to create a closed curve without having houdini automatically create a surface from it?

If you want to create e.g. triangle, and with Curve SOP draw two sides, then check Closed Curve, it draws third side. Then just append Ends SOP and set Close U to Unroll.

For Nurbs Curve you need to append Join SOP (check Wrap Last to First) then append Ends SOP (with unroll option)

Thanks pezetko, that was quick and helpful