Hex#ProofOfWork seems like a sensible alternative to #Google #reCAPTCHA to avoid misuse and spam and still enable #anonymous usage.
hackint IRC uses #hashcash for example: https://hackint.org/transport/tor#Anonymous_Account_Registration
Jonkman Microblog is a social network, courtesy of SOBAC Microcomputer Services. It runs on GNU social, version 1.2.0-beta5, available under the GNU Affero General Public License.
All Jonkman Microblog content and data are available under the Creative Commons Attribution 3.0 license.