I imagine that they are only for OLPC because of some copyright agreement. Anyway it would be nice that they were available to the rest of the Internet (or may be they are and I did not read well the news).
The reason that these are finally available for the OLPC is because they are now all available in EPUB format, and the Read Activity on the OLPC has been updated to handle EPUBs.
In the past, the OLPC could not display archive.org pdfs, due to the specific PDF encoding used (MRC-compressed pdfs with jpeg2000 layers).