First of all I KNOW there is this thread:

I have the same issue as Eric with a fresh new insall of rihio 5.4.2 evaluation on MAc Os (valid until end of August 2018). Did you validate your evaluation license? If not, please run ValidateLicense, then Quit and re-launch Rhino. Grasshopper should be available until the evaluation period expires.

But it's closed for new comments.

1. Rhino 6 for Mac with Integrated Grasshopper As Architosh has written in the past, the big news about Rhino 6 was the integration of Grasshopper, the industry’s leading algorithmic-aided design (AAD) or node-based visual programming tool.
2. Perform tasks in Rhino or Grasshopper that you don't have access to in the standard set of Rhino commands or Grasshopper components. Generate geometry using algorithms. Many, many other things. It is a programming language after all. Both the Windows and Mac versions of Rhino contain support for the Python scripting language.
3. The v23 & v24 of Grasshopper – Archicad Live Connection supports Rhino 5 and Rhino 6 on both platforms (Win & macOS). On Windows both v21,v22 of Grasshopper – Archicad Live Connection supports Rhino6. On macOS both v21 and v22 of Grasshopper – Archicad Live Connection supports Rhino5. They don’t support Rhino6 WIP.

I'm making a new one because I just received this email:

______________________________________________________________________

As most of you know by now, Grasshopper will be included in Rhino 6 for Windows. We are almost finished with the Grasshopper in Rhino 6 development and you are invited to try it.

There are many enhancements, including:

Grasshopper For Mac Rhino Xp

• High DPI displays are now supported.
• Compatible with existing Grasshopper plug-ins.
• New components including Make2D, Bend, Flow, Maelstrom, Splop, Splorph, Stretch, Taper, and Twist...
• GhPythonis now included. It features its own GHA compiler and a major node-in-code speed up.
• Stable development target: Your plug-ins continue to work each minor Grasshopper upgrade.
• RhinoCommon enhanced: More Rhino core functionality is accessible from within Grasshopper.
• Developer documentation is online with guides and API references.

Now:

1. Download the current Rhino WIP for Windows
2. Try all your existing Grasshopper definitions
3. Report any problems you find here...

We want to make sure this new Grasshopper works for you. If you have any issues, David needs to hear from you very soon.

Thank you,

- Bob

Rhinoceros and Grasshopper – developed by Robert McNeel & Associates – are considered market leaders in industrial design modeling and algorithmic design.
Now, designers have various options to connect Archicad’s professional BIM work environment with the modeling power of Rhino and Grasshopper.

Prerequisites

Before installing any connections, make sure that Archicad, Rhinoceros3D and Grasshopper is installed on your computer.

Table of Contents

Grasshopper – Archicad Live Connection
Rhinoceros Import/Export Add-ons
Rhinoceros – GDL Converter

Grasshopper – Archicad Live Connection

Important Notes:

• The v23 & v24 of Grasshopper – Archicad Live Connection supports Rhino 5 and Rhino 6 on both platforms (Win & macOS).
• On Windows both v21,v22 of Grasshopper – Archicad Live Connection supports Rhino6.
• On macOS both v21 and v22 of Grasshopper – Archicad Live Connection supports Rhino5. They don’t support Rhino6 WIP.
• Grasshopper – Archicad Live Connection is not compatible with Archicad STAR(T) Edition.

Rhinoceros Import/Export Add-ons

Important Notes:

Rhino 6 format is not supported in the built in Rhinoceros Import/Export function in Archicad 22.

From Archicad 20 on these Add-Ons are part of the Archicad package. In Archicad 19 and 18 install these free Add-ons to enable Archicad to import and export models using Rhino’s native (.3dm) file format.

Import Rhino Model to Archicad

Rhino Importer Add-on enables Archicad users on both the Mac and Windows platforms to pass on the model or part of the model produced in Rhino to Archicad. This Add-on, available for Archicad 18 and 19, enables you to open or merge native Rhino (*.3dm) files directly in Archicad.

Export Archicad Model to Rhino

Rhino Exporter Add-on enables Archicad users on both the Mac and Windows platforms to pass on the model or part of the model produced in ARHICAD to Rhino. This Add-on, available for Archicad 18 and 19, enables you to save the Archicad 3D model as a Rhino file (*.3DM).

Rhinoceros – GDL Converter

Install these free plug-ins to convert Rhino models to native Archicad GDL elements – standalone objects (.gsm) or library containers (.lcf).

Please watch this video to find out more about how to install the necessary plug-ins, and how to import a model created in Rhinoceros into Archicad as native GSM objects. The video first presents the “Single Object Import” workflow using.gsm files and then the “Complex Structure Import” using .lcf files.

Steps to import Rhinoceros models to Archicad

Download and install plug-in for Rhino

Download and launch this “GSM-LCF exporter for Rhino 5” Rhino plug-in to be able to save/export Rhino models.

GSM-LCF exporter for Rhino 5

Choose import method

Depending on the size of the Rhino model, choose one of these two import methods:

Single Object Import to Archicad

Use this workflow to import small-sized single objects or groups of small objects saved in GSM format to Archicad.

Save Rhino model as GSM file

In Rhino, select the model or its parts you want to export and save them as GSM Object File using the “GSM-LCF Exporter for Rhino 5” plug-in. Go to File/Save or File/Export Selected and in the upcoming dialog choose the “Archicad GDL Object” file type (extension .gsm).

Place the object in Archicad

In Archicad, add the object to the Embedded Library, then place it into the Archicad project as an Object.

Complex Structure Import into Archicad

Use this workflow for larger and complex Rhino models to convert them into a set of (smaller) GDL objects. This process enables the user to retain separate logical parts within the same model while providing a functionality to monitor and easily update the imported Rhino models in Archicad. The LCF option is also advised to enable Archicad’s performance optimization algorithm to work seamlessly on an imported large Rhino model.

Save Rhino model as LCF file

In Rhino, select the object(s) you want to export as a reference model to Archicad. Go to File/Save or File/Export Selected and save them as LCF Container File using the “GSM-LCF Exporter for Rhino 5” plug-in. In the upcoming dialog choose the “Archicad GDL Object Library” file type (extension .lcf).

Download and install the “Rhino LCF Observer” Add-On for Archicad

Rhino LCF Observer 20 for Windows

Grasshopper For Rhino 5 Mac

Rhino LCF Observer 20 for Mac OS X

Rhino LCF Observer 19 for Windows

Rhino LCF Observer 19 for Mac OS X

Grasshopper For Mac Rhino 660

Rhino LCF Observer 18 for Windows

Rhino LCF Observer 18 for Mac OS X

Grasshopper For Mac Rhino 6

Place LCF model in Archicad

Grasshopper Software Rhino

In Archicad, add the LCF file as a Linked Library in Library Manager, then place it into the Archicad project as an Object. Using the “Rhino LCF Observer” Add-On you can place all objects from the LCF files, and/or to update any placed instances as needed.

Guides for Rhinoceros-GDL Converter