The existing tech blocking system lives in the experimental options tab (modoptions.lua lines 1766-1832). Seth authored it and has moved on from maintaining it. C3BO has built a TechCore gameplay variant on top of it with active community testing, including dedicated "tech core" buildings, no-sharing + tax economy settings, and a per-team tech research mechanic.
The system has known bugs (click/selection issues, debug spam) and no integration with the modes/policies architecture from the sharing_tab branch. This document plans the migration.
For background on the Controller/Policy architecture, see Game Controllers & Policies.