The internal build is an unofficial patched version which passed our internal automated tests, however it is not recommended for production. It is available for commercial license holders only.
Kendo UI Complete for ASP.NET MVC offers a complete internal build zipped package (including local demos, source code, etc.) and a hotfix zip package, which is a stripped-down version of the former and does not include demos or source. Use the latter in case you don't need the additional resources, as its size is significantly reduced (26MB vs 4.2MB).
I hope this explanation helps.
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