Philip would like the only online copy of the books to remain at philip.greenspun.com so as not to confuse google.
But, to quote Philip:
"On the other hand if they want to make something substantially new, using my text as a starting point, and credit me and release the new thing under the Creative Commons license that would be fine."
In that case, Mike or anybody else, could you at least make sure you
personally have good backups of those online books, so if Philip
should ever be hit by a bus (crash his airplane, or etc.) and his site
go dark, the content won't be lost?