We understand that our typical customers may have a design PC in the office or at home and another in the workshop that's connected to the CNC machine. So we license the software on a per user basis that allows the software to be used on any one PC at a time. So to answer the first part of your question, Yes it is acceptable for you (a single user) to use the software on multiple PC's.
The second part of your question implies that your Sales person may need to use the software at the same time as you are designing, and this requires a second user licence to be purchased.
The software is licensed using a Security Code (no hardware lock) that is specific to each customer.
I hope this makes sense and answers your question.