Update the public domain dedication information to indicate that it applies to all repositories in the organization, and requested on a PR.

Author: gkellogg

README.md

@@ -438,7 +438,7 @@ This repository uses [Git Flow](https://github.com/nvie/gitflow) to mange develo
   enough, be assured we will eventually add you in there.
 * Do note that in order for us to merge any non-trivial changes (as a rule
   of thumb, additions larger than about 15 lines of code), we need an
-  explicit [public domain dedication][PDD] on record from you.
+  explicit [public domain dedication][PDD] on record from you, which you will be asked to agree to on the first commit to a repo within the organization. Note that the agreement applies to all repos in the [Ruby RDF](https://github.com/ruby-rdf/) organization.
 
 ## License