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Paid support, tools, there're plenty of companies which follow this business model. Extjs, Vaadin, Typesafe, etc. I understand that they want to make a money, however, using their license is unacceptable risk, especially taking into account there're comparable alternatives. I'd rather use GWT/TypeScript/Scala.js, than proprietary framework which I won't be able to work with if they changed license to something unacce…
If you worry about such hypothetical licence or price changes, you could also contact the company and negotiate a custom licence/contract.
The better option is to use, the most popular open source tool which in this area is GWT or TypeScript.