To install regular Handsontable version run npm install handsontable and for PRO it is npm install git+ssh://git@git.handsontable.com:handsontable/handsontable-pro.git.
This setup does not work. It assumes that all development environments have SSH key required to access the package. It makes extremely difficult to integrate the package in the CI and make it available to every developer working with the project.
Use license to control package usage. You are not going to stop people from using illegally your package (just search online, there are plenty of websites offering to download your script pro version). It seems pointless restriction thats hurting only the paying users.