Self-hostable software: CAPTCHA Services (4)

Cap is a lightweight open-source CAPTCHA alternative that uses SHA-256 proof-of-work and JavaScript instrumentation challenges.

pyLoad is a lightweight, pure-Python download manager with a web UI and plugin ecosystem for automating downloads from hosters, cloud drives, and other sources.

Artalk is an open-source, self-hosted comment system for blogs, websites, and web applications.

mosparo is a self-hosted spam protection tool for online forms that replaces CAPTCHA with rule-based detection.