It appears that there has been a change to the licensing, at least with respect that the Apache 2.0 license is in the license/ folder. The E204_E300 license document in the 1.3 releases is dated 2012-09-06, while the E204_E300 bound to the download site is dated 2013-04-26.
I'm not a lawyer, and I don't speak as a legal representative of Esri (the license speaks of a "signed" alternative anyway), but to the best of my understanding, the E204_E300 license is intended to protect API distribution (the include files and link libraries) but that the runtime libraries (in the Windows distributions, the files in the "bin" directory, not the "lib"), are freely distributable with applications that use them. That is, you can code with the API, and make royalty-free applications that reference and distribute the runtime DLLs, but you cannot redistribute the API itself without written permission. If you distribute source that could be compiled using the SDK, then others would need to license the SDK themselves in order to compile your source. Which is all pretty much standard in the COTS world (except for the runtime distribution, which is atypical [and pretty cool]).
I've contacted Contracts to get clarification on this issue.
- V