While this is mostly true, it's worth noting that this is part of a push to make Core easier to build and use, which we hope will encourage more people to use it. (And enable others to contribute.) There's still a ton of work to be done in that regard, but this release, at least, includes a Linux build script, and the libraries which are necessary for building Core.
Also, this release includes Async (our concurrency library), which is a much more recent release (October 2011). If you'd like more information about Async, there's Ron's blog post announcing the release [1], and also a previous comment of mine with some very basic sample Async code [2].
What was the initial motivation for writing an alternative "standard" library? Is it self-sufficient or does it build new frameworks onto of OCaml's standard library?
The std-lib in OCaml's official release by INRIA is very basic and not enough to be used in medium/large projects, and some people would rather call it "base-lib" instead of "std-lib" . Two major libraries can be used as an alternative, i) Jane Street's Core libraries. and ii) the comunity-driven "Batteries included".
First, I think for beginners the std-lib is fairly enough for basic learning tasks. Choosing a library is something one should consider only after he has gained some insight of the language.
Second, As no better than someone "just starting out with OCaml" myself, I'd like to redirect you to this page on StackOverflow for a comparison between Batteries and Core:
Choosing a library is something one should consider only after he has gained some insight of the language.
Well, like I said, I've tinkered with OCaml in the past and have a reasonable idea what it has to offer. While I still have a lot to learn before I can properly make use of OCaml idioms and such, I would prefer if I didn't have to relearn the library as soon as I get to a level where I can write real programs. From the link I see that Batteries is backwards compatible with the standard library, so perhaps its the better one to start with for a beginner.
I'm really not the right person to be answering this. I haven't been at Jane Street that long, and I have no experience programming OCaml without Core. You'll likely get a much better answer on the mailing list: https://groups.google.com/forum/#!forum/ocaml-core. (I've also posted a link there to this discussion already, so hopefully someone will come by and give you a better answer.)
Probably the biggest difference between Core and the INRIA (default) standard library is that Core itself is mostly written in OCaml. This has many benefits: code is less verbose, easier to read, it's easier to verify correctness, etc.
Also, this release includes Async (our concurrency library), which is a much more recent release (October 2011). If you'd like more information about Async, there's Ron's blog post announcing the release [1], and also a previous comment of mine with some very basic sample Async code [2].
[1] https://ocaml.janestreet.com/?q=node/100
[2] http://news.ycombinator.com/item?id=3278532