Yes, SWAT-CUP from 2w2e has to be purchased, it is a non-freeware and 2019 is restricted to certain features. Another way of having it as a nature of freeware is achievable by using R-SWAT, a calibration tool with R-programming language w or w/o. GUI, the same sort of SWAT-CUP by 2w2e. This calibration tool, guidelines and other references are available on SWAT Texas A&M's official website (Software section), a GitHub, a Youtube channel and an R-SWAT community - google group. Please do try them, the software material can also be cited during research work publications in leading journals. Many have used and I'm to a person/researcher who used the tool for my SWAT model calibration, under the work of Inter-Basin Water Transfers and River Inter-linking in the Cauvery River Basin, India!
Sincerely,
Post-matric Scholar in Hydrology and Water Resources,
Graduate Engineer in Civil,
Student Member from Institution of Engineers, India.