Straight onto your questions:
1) Usually we don't compare our components with other commercial vendors publicly. It is a bit unethical in our opinion. If you have specific questions however you can open support ticket and we will gladly answer you!
2) Indeed you can use our trial version forever - just the support will expire.
3) In our opinion WCF RIA Services is definitely the way to go. You will get fast and lightweight RESTful service with built-in support for paging, sorting, filtering, grouping, CRUD, etc. In most of scenarios you will not need to write code (RadDomainDataSource!).
4) Please check this page fore more info.
the Telerik team
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