I wondered when someone would ask such a question.
Their copyright is limited to the presentation, as are most publishers copyright, and this tends to be only 25 years to allow authors to get their works republished if the original publisher refuses. So copying and republishing their edition which is actually a facsimile (photographs of pages and usually poor quality.) would fall foul, I am not sure that the 25 years applies since more recent changes in copyright law and in any case publishers rights vary from country to country.
In the glass study I convert 'the original books text' to text, add annotations as available or when comments get made, and restore all images to as good as new. I preserve pagination (in most cases) to allow reference to the original, but I do ask members for the addition of 'Courtesy the Glass-Study'. All of my restorations are subject to copyright and have a minute alteration to detect unauthorised re-use. Glass-Study members can make reasonable use of the sites images on their web-site, except for licensed works, and if wanted for a book the original restored scans are available at a nominal fee. Where I reproduce copyright material I either get a license to do so or convert the text to an paginated index so that searches will be able to find references in books that can then be purchased from booksellers in order to find out what those references about. As it is a non-profit venture I usually get free licenses and once I have established it part of the proceeds will be used for costs and the remainder paid into a charitable fund being set-up to preserve glass web-sites. Recovering the costs of the glass-study is unlikely without sales of images for use in publications and I expect to have something in excess of 100,000 glass images available after stage 1 of the development c.2012.
After 2012 I do have additional plans to create additional income streams to help build the fund and once that charity is established the first year subscription officially starts and fees for founding members will be fixed but new members will have to pay more. I have paid considerable sums for legal advice on copyright complexities that affect what I am doing and also considered the impact on antiquarian book-sales, which I consider to be miniscule as I can only digitise a couple of hundred works with a retail value of around 20,000 Euros. Equivalent to 600-700 subscriptions.
The basic philosophy is to make material easily searchable, annotations allow highlighting of errors or indication of later research and to fund the preservation charity. Were I to make the site public it would not be possible to obtain licenses where needed. Organisations doing a similar thing but trying to cover the costs charge typically from 1,000 dollars per annum to cover the costs involved and they have no connected collaborative research facilities, the studies are currently primitive and that will be addressed in Stage 2 after 2012.
My personal commitment will continue to at least 2012 after which I hope to partner with others and provide facilities that researchers can get a small income from material that is not cost effective to publish in print.