Product review: Inside open source AJAX toolkits
By that same token, some of the grassroots projects are growing more commercial. Full support and training for the Dojo Toolkit, for instance, can be found from companies such as SitePen, while companies such as WaveMaker are building visual design tools that revolve around Dojo. These companies typically employ people who are contributing to the Dojo project. Furthermore, Dojo is supported by a more official foundation that pays a number of people with cash from major companies such as IBM. Dojo is not a small, part-time operation any longer.
Dojo isn't the only operation growing quickly. Ext, a fast-growing toolkit, offers full commercial licenses to its code that free you from the GNU LGPL. You might begin using the code as a library but start paying once you need the greater freedom of a full license.
A more difficult question to answer may be the style of the project. While all of the projects aim to be efficient layers that smooth over the differences between browsers, there are now significant differences between the coding styles of the groups. If you've got opinionated developers on your team -- and who doesn't? -- they're going to find a way to be wildly enthusiastic about one project, while sneering at the style or technique of the others. Some groups are pushing simplicity and size, while others are adding features such as modularity. People are serious about their projects, and flame wars are common.
There are also many simpler examples of cross-pollination. All of these projects watch each other carefully, and the licenses allow a great deal of mixing and matching. If one group happens to find a clever way to code a particular function, it often appears in others within a few weeks. For that reason, the problem of choosing one framework may not be as important as it seems. The good ideas and best practices will probably make their way to all of the projects, one way or another.