MIT is Not a Copyright Shield

License-safe ≠ expression-safe. A critical review caught what the research missed.

Date: 2026-08-16 Session: Experiment 006 research (falling-block game) Status: Adopted as research rule

The mistake

Researching a Tetris-style experiment, the agent (correctly) found an MIT-licensed original (jakesgordon/javascript-tetris, 733★, MIT verified) and returned a BUILD verdict — assuming MIT = safe to fork. The assumption was incomplete: the MIT license covers that code, but the code's visual expression can still embed third-party protected expression. The Tetris Company's protected elements live in the code's look-and-feel, not its license file.

The evidence trail

The research verdict (what looked right)

"Original: jakesgordon/javascript-tetris — vanilla JS/HTML5, explicit MIT license (LICENSE file + README), 733★/887 forks. Verdict: BUILD. Ship under a non-trademarked name; falling-block mechanics are not copyrightable."

Verified independently: MIT confirmed, 733 stars confirmed, no hallucination. The license claim was true — but insufficient.

The critical review (the catch)

"The binding precedent isn't trademark — it's Tetris Holding v. Xio (2012), which made the 10×20 board, ghost piece, next-piece preview, and color-on-land copyrightable expression. Forking jakesgordon's MIT code as the visual-layer base embeds the exact expression the court protected."

Score: 6.0/10 — ITERATE, below the 7.0 gate, failed deterministic check (legal risk model incomplete).

The verification (independent)

"This includes the twenty-by-ten square game board, the display of a block's 'shadow' where it will land, and the display of the next piece to fall." — Tetris Holding v. Xio Interactive, D.N.J. 2012

The court protected the 20×10 board, the ghost/shadow piece, the next-piece preview, color-on-land, and the junk-block start. Mechanics remain legal; expression is what's protected.

The fix

Build the visual layer from scratch with deliberate differentiation: different board dimensions, reworked or absent ghost piece, distinct art style — never fork the visual expression, even from MIT code.
Never reference the trademark — ship as "falling-block" with generic art and a generic name.
Add a research gate: before BUILD, the agent must check not just the license of the original but whether the expression is protected (court precedent for the genre). License-safe ≠ expression-safe.
Prototype the twist first (Banked Clears: rows persist until a bank key clears them with a burst multiplier) before committing to the full build — validate the mechanic, then differentiate the expression.