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 unacceptable (for example, charge per server or whatever).

ExtJS is GPL with paid commercial license, so essentially the same model as WebSharper. They even explicitly forbid to start developing a prototype in the open and then buy a license for it, which WS doesn't.

If you worry about such hypothetical licence or price changes, you could also contact the company and negotiate a custom licence/contract.

Usually, such companies have quite high price for such contracts and I think it's not worth is. While technically it might be superior, it has small user base, smaller talent pool to hire from, less books/documentation. All this happens because people want to make money in an old fashioned way.

The better option is to use, the most popular open source tool which in this area is GWT or TypeScript.