If you are providing custom software development services to the client and want to include our product as part of developed solution for one client, then your service is similar to work for hire, and you can be treated as an employee of the client (in this particular situation and for licensing purpose only). Consequently you can purchase a license for our product as if the client purchased it, i.e. for client's name and according to client's further plan to distribute the created software.
If you are providing custom software development services to many clients and want to include our product as part of developed solutions for different clients, the license should be purchased for each client as described above. Also, in such scenarios you can become our reseller or purchase several licenses (for different clients) with discount. In the latter case please contact us using one of contact options.