Three generations of CogVideoX, three degrees of closing: Apache 2.0, a revocable licence, then no weights at all

Z.ai's video line has shipped three generations in two years, and each one has been harder to use freely than the one before. The catalogue now holds all three, so the sequence can be read in one place. On 6 August 2024 the producer published CogVideoX-2B, its first video model with downloadable weights: six seconds of 720x480 at eight frames per second, from 4 GB of video memory in the diffusers library and 3.6 GB with INT8 quantisation. It shipped under the producer's own restrictive document. Three weeks later, on 27 August 2024, one entry in the project's changelog did two things at once. It announced the larger CogVideoX-5B — same six seconds, same 720x480, about 5.6 billion parameters in the video transformer instead of 1.7, from 5 GB of memory in BF16 — and, in its closing line, moved the 2B to Apache 2.0. The bigger model did not get the same treatment. It went out under the CogVideoX Licence, which grants a copyright licence that is expressly revocable, permits academic use freely, and requires commercial users to register with the producer and stay below one million service visits a month. So the small model became genuinely free on the exact day the large one arrived without that freedom. That is the opposite of the usual pattern, where a producer opens the small model as a sample and holds the flagship back — here the flagship was released, but on terms the smaller model had just escaped. The third step removed the choice. CogVideoX-3, launched in July 2025, has no public weights at all. It is a hosted product: up to 3840x2160, five or ten seconds, 30 or 60 frames per second, an optional generated soundtrack, a flat $0.20 per video. Whoever built on the open versions cannot follow the line forward — they can only start again on someone else's weights, or pay per clip. The open two are not abandoned. In the 30 days to 4 September 2026, CogVideoX-2B was downloaded 20,387 times and CogVideoX-5B 17,161 times on Hugging Face — two years after release, and a year after the generation that replaced them stopped being downloadable at all.