The Internet History Sourcebooks Project constitutes an attempt to compile a plethora of online sources of a historical nature that can be used for educational and research purposes.  Most of the included sources are in the public domain, and those that aren’t are at least copy-permitted.  Now, insofar as  the sources included in these compilations are included in the public domain, there’s no real issue of copyright violation.  The legality of offering such sources to the public, then, is easily defensible.  Furthermore, since these sources are used for educational purposes (as opposed to commercial purposes), and since they’re of a factual nature, there’s reason so conclude that the Internet History Sourcebooks Project is protected under free use, and therefore doesn’t constitute any kind of copyright violation.