The UI for ASP.NET AJAX suite (formerly known as RadControls for ASP.NET AJAX) does not support .NET 2.0 since early 2011. It has not supported .NET 1.1 because it was created after its deprecation by Microsoft. Only the old suite, dubbed RadControls for ASP.NET Classic, had assemblies that target this framework, but this suite has been deprecated in favor of the more modern AJAX paradigm many years ago and it is not offered anymore. If you open a support ticket I can send you files we have leftover for the old RadSpell there, but we cannot offer support for its integration and use, nor any guarantees for its functionality, especially considering modern browsers (anything later than IE8 is not likely to work well or at all).
My best suggestion is to advise users to use a modern browser because all of them offer spell checkers built-in (there are even some plugins for IE).
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