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Reference — Free asset licences, and what they actually permit

REF104 · r1 · 2026-09-06 · Reference Researcher · Reference, not a design proposal. Not legal advice. First revision. Written because Design Document r9 §14 now carries a live asset decision, and the Brief requires that "any shortlisted asset needs its actual source, creator, terms, and intended use recorded." This page records what the terms mean. Sources read: Design Document §§14, 17 and its asset-check record, Brief asset policy, Reference.

Scope, and a limit worth stating first. I am not a lawyer and this is not legal advice. Everything below is quoted from a licence steward's own published text or a platform's own terms, with a link. Where a question needs a lawyer — and one of them does — the page says so instead of guessing.

It also decides nothing and shortlists nothing. No asset was downloaded. Suitability, style fit and quality are not assessed here and are not this role's call.

1. The lead's asset check, independently confirmed

Design Document §14 records a read-only check of two sources and is careful to claim only what it saw. I re-fetched both, because a licence claim is exactly the kind of fact worth having two people look at:

  • Kenney's "Top-down Shooter" pack states "Creative Commons CC0" and 580 files, described as top-down 2D sprites including tiles, furniture and zombie-style figures (kenney.nl/assets/top-down-shooter). Confirmed — independently fetched 2026-09-06, and it matches the document's record exactly.
  • OpenGameArt hosts work under one of CC0, CC-BY 3.0/4.0, CC-BY-SA 3.0/4.0, OGA-BY 3.0/4.0 or GPL 2.0/3.0, chosen per asset by its uploader (OGA FAQ). Confirmed. §2 below is why that per-asset detail is the important half of the sentence.

The document's hedging is right and worth keeping: it says the pack is "a plausible candidate… subject to a suitability check nobody has done yet", and that nobody has inspected the sprites in the engine.

2. What each licence actually permits

All rows quoted from the steward's own summaries: Creative Commons, CC0, OGA-BY FAQ.

Licence Commercial use Derivatives Attribution Share-alike
CC0 Yes Yes None required — "No attribution required (unless the user chooses to give it)" No
CC BY Yes Yes Required — "Credit must be given to you, the creator" No
CC BY-SA Yes Yes Required Yes — "Adaptations must be shared under the same terms"
CC BY-ND Yes No — "in unadapted form only" Required n/a
CC BY-NC, BY-NC-SA, BY-NC-ND No — noncommercial only varies Required varies
OGA-BY 3.0/4.0 Yes Yes Required (CC-BY-based) No
GPL 2.0/3.0 Yes Yes — Yes, with source obligations

CC0 waives "all copyright and related rights in their works to the fullest extent permitted by law." It is the only row above that imposes nothing on you at all.

OGA-BY is "a license based on CC-BY 3.0 that removes that license's restriction on technical measures that prevent redistribution of a work" — i.e. CC-BY minus the anti-DRM clause, which matters if a work ships inside a packed archive. Attribution still applies.

GPL is the row to take advice on rather than a chance. It is on OpenGameArt's list, it carries share-alike and source obligations designed for software, and how those obligations apply to art shipped inside a commercial game is exactly the question a lawyer should answer. Simplest safe rule: do not shortlist GPL-licensed art without that advice.

3. Two traps that bite this project specifically

Design Document §14 proposes, as the cheapest art route, a humanoid Flood "tinted and size-varied from a free pack." Tinting and resizing produce an adaptation, and that is precisely the axis the licences differ on:

  • CC0 — fine, no obligations.
  • CC BY — fine, with attribution.
  • CC BY-SA — permitted, but "adaptations must be shared under the same terms." Your derived sprites would carry CC BY-SA.
  • CC BY-ND — not permitted at all: "unadapted form only."
  • any NC variant — not permitted, because a Steam release is commercial.

Since OpenGameArt's licence is chosen per asset by its uploader, "we'll use OpenGameArt" is not a licence decision; each asset is. The pack actually named so far, Kenney's, is CC0, which is the row with no trap in it — that is a genuinely fortunate starting point rather than a general property of free assets.

3.2 "Free" on the Unity Asset Store is not "free" in the OpenGameArt sense

The engine is Unity, so this is the likeliest confusion, and it is a licensing difference rather than a price one. Free-of-charge Asset Store items are still governed by the Asset Store Terms of Service and EULA:

  • You may "incorporate the Asset, together with substantial, original content… into an electronic application or digital media" and monetise it within that product.
  • You may not "use, reproduce, duplicate, publicly display, publicly perform, copy, modify, adapt, translate, prepare derivative works of, distribute, transfer, license, sublicense, rent, lease, lend, sell, trade, resell, or otherwise commercialize or monetize any Asset except as expressly permitted."
  • "Extension Assets" (Editor Extension, Scripting, Services) are "licensed on a per seat basis and may not be shared or used concurrently on more than 2 different computers" (§2.3.2).
  • "Restricted Assets" carry separate terms which "will control" — typically where open-source components limit distribution.
  • The terms also prohibit using Assets "for purposes such as training an artificial intelligence or machine learning model without the express consent."

So an Asset Store freebie is a licence to use, not a public-domain dedication. It cannot be re-shared, and it is not interchangeable with a CC0 pack in the record the Brief asks for.

4. Steam's AI-content disclosure, since the project bans AI art

The Brief forbids AI-generated art outright. That makes Steam's disclosure regime easy to satisfy and worth knowing before the store page is written:

  • Submission requires disclosing generative AI in two categories: "AI to generate content for the game" and "AI content generated during gameplay."
  • The first category explicitly covers content in the game, on its store page, or in marketing materials — not just what ships in the build.
  • "AI powered tools" used for workflow — the example given is code-helper software — do not require disclosure.
  • Disclosure appears publicly on the store page, in an "AI Generated Content Disclosure" section.
  • The policy was introduced in January 2024 and significantly rewritten in January 2026 to focus on player-facing content rather than development tooling.

Sources: Game Developer (January 2026 rewrite), VGC, GeekWire (original announcement). These are press reports of Valve's Steamworks posts; I could not fetch Valve's own page directly — its store-news URL returned only navigation chrome. Treat the wording as reported rather than quoted from the primary, and confirm against Steamworks before anything is submitted.

Bearing on this project (inference). A project that uses no generative AI for assets answers "no" to both categories and carries no label. Two details are worth carrying anyway: the store page and marketing are in scope, so the ban has to hold for the capsule art and trailer too, not only the build; and the tools exemption is about workflow, not output, so the line to watch is whether any tool's output ships. Neither is a decision for this page.

5. What the Brief's record needs, per asset

The Brief asks for "source, creator, terms, and intended use." From §2 and §3, four additions make that record actually checkable later:

  1. The licence name and version, copied from the asset's own page — not from the host's general FAQ. OpenGameArt is per-asset; a site-level statement proves nothing about one file.
  2. A direct URL to the asset page, and the date it was read. Licences on user-upload sites can be edited by the uploader.
  3. Whether the intended use is a derivative (recolour, resize, re-cut). §3.1 is only a problem for derivative use, so recording the intent is what makes the licence answerable.
  4. Attribution text prepared at shortlist time, for any BY row. Attribution is cheap to satisfy on the day and expensive to reconstruct at ship.

Kenney's pack, as the one asset checked so far, needs only rows 1–3: CC0 requires no attribution, though crediting is normal courtesy and costs nothing.

What this page does not claim

Not legal advice, and not a substitute for the licence texts, which govern. No asset is shortlisted, recommended, downloaded, or assessed for suitability, style or quality — none of which is this role's call. No claim that any pack fits this game. No claim about Valve's current policy beyond what the cited reports say, since the primary page could not be fetched (§4). The GPL question in §2 is explicitly left open for a lawyer rather than answered.

Sources

Bookkeeping

Method. Public licence texts and platform terms, fetched read-only on 2026-09-06. Nothing was downloaded, built, prototyped or tested. Kenney's licence and OpenGameArt's licence list were re-fetched independently rather than taken from the Design Document, and both matched what that page recorded.

Weakest material on this page, flagged in place: §4's Steam wording is from press reports of Valve's own posts, because Valve's store-news URL returned only page chrome. Everything else is quoted from a steward's or platform's own page.

Corrections. Kill any statement here with a counter-source and it goes. If a lawyer contradicts §2 or §3, the lawyer is right.