Project products delivered via volume licensing programs are licensed on "per Device"" model similarly to other Office products.

• Project Professional enables you to collaborate with others to easily start and deliver winning projects. Includes a Project Server CAL.
• Project Standard enables you to keep projects organized and on track.

Project Server is licensed using a server/CAL (client access license) model. Microsoft Project and portfolio management solutions require a Project Server license for each running instance of the software, and CALs are required for each person or device accessing a Project Server. 

• Project Server helps organizations get started, prioritize project portfolio investments, and deliver the intended business value.
• Project Server CAL version not lower then Project Server is required for each user or device accessing Project Server.

We can deliver you Project Server & PRoject Server CAL's on Request.

Customers should review the official licensing documentation and consult with a Microsoft licensing specialist to ensure compliance and determine the most suitable licensing approach for their specific requirements.

Additional materials from Microsft:

Licensing Project Server 2019 on-premises