a plan to collaborate in digitizing 1.5 million pages of rare and ancient texts, most dating from the 16th century or earlier. All this will become available on-line and most likely a copyright will be claimed on these scans.
Sadly some countries claim that "sweat of the brow" is enough reason to prevent pictures or scans of works that are obviously in the public domain to become available as public domain.
The usability of scans is however limited. It is only once the texts in such scans have been transcribed that you can easily read it and research it.
Both scanning and transcription is a lot of work. Both involve a lot of sweat of the brow. Where scanning precious books and documents requires specialists and equipment, transcription takes people willing to type the texts that they see in the scan.
When rights are reserved on scans using the "sweat of the brow" argument, the texts in these scans cannot be claimed in this way. These books are all in the public domain and transcribing them exactly from these scans serves one purpose really well. They establish the provenance between the original sources that are represented in these scans and the texts people refer to.
Having the original text exactly transcribed is one way of dealing with problematic translations and the resulting problematic interpretations. Having such transcriptions in Wikisource is well worth it.