It's not really impossible to conceive that they might actually have a valid claim.
It's not really impossible to conceive that they might actually have a valid claim.
Unless recreating non-patented work from memory is actually forbidden? That would be horrible.
Here lies the black magic of the Non-Compete Agreement.
Nevertheless, this doesn't look like a Non-Compete Agreement violation, or we would probably have seen those words in the article. My guess is, Carmack haven't signed one (75% probability).
It's essentially writing new code looking at your old source code, and hence directly derivative of work that Zenimax has a reasonable claim to.
It is also possible to work back from first principles. Heck, many Free Software was written like that: by rewriting the proprietary parts, possibly one by one.