Currently we are working with MS CRM 365 On-Premise and there is a requirement came from the client to develop a portal for the Customer as well as Vendors. We have heard about the MS CRM 365 Portal option which we can enable and design portal as per the requirement.
As we are using On-Premise we knew that we can have option of Adx-Portal where we would require the valid license, although tried to search and found that Microsoft release the Microsoft Dynamics 365 Customer Engagement Portals Source Code, the download contains the self-hosted Portals which are available for Dynamics 365 On-Premise. This will allow you to customize the portals per your requirements and deploy then to Dynamics 365 (On-Premise) as well as Dynamics 365 (Online).
The portals are compatible with the Online and On-Premise version 8.1 and later. The important thing to note is that this source code is provided to customers that are unable to deploy portals in an online environment, and are willing to maintain the portals code internally. Microsoft is not planning on supporting this code, which is also why it is provided under the open source license, and at the point of writing this, there are not acknowledgements of whether or not this will be supported in the future.
The download contains the solution files, the source code and the deployment instructions of the source code. The integration with the Portals web application can be implemented using an internal/organizational IIS server or using Microsoft Azure.
You can download the portals from the following link:
You can configure the Portal for your organization with the help of deployment instructions document provided and use the open source portal.
Hope this information will helpful.