Open source It use as standalone application for generation of CAD models, their preparation for numerical calculations and post-processing of the calculation results.
http://www.salome-platform.org

Easy to Create/modify, import/export (IGES, STEP, BREP), repair/clean CAD models
Supports interoperability between CAD modeling and computation software (CAD-CAE link).
Mesh CAD models, edit mesh, check mesh quality, import/export mesh (MED, UNV, DAT, STL)
Makes easier the integration of new components into heterogeneous systems for numerical computation.
Easy to Handle physical properties and quantities attached to geometrical items
Display computation results (scalar, vectorial)
Provides a generic user-friendly and efficient user interface, which helps to reduce the costs and delays of carrying out the studies.
Reduces training time to the specific time for learning the software solution based on this platform
Manage studies (create, save, reload)
Provides access to all functionalities via the integrated Python console.

This looks very interesting. Thanks!

V7 !
http://www.salome-platform.org/

It can be used for convertion from nurbs to poly?

Of course yes! :)
Here a volume from Moi exported in format Stp or Igs ---> so Nurbs inside Salome
Export from Salome in STL
Import STL in Meshmixer :)
On the right Salome Box dialog export with formats possible
On the left MeshMixer screen

I can not see here .obj?

It's not a program for make video game so obj is not provided!
But if you have STL you can convert it in obj with any other 3D party application :)