Is the ARC Theory pseudoscience?
Judge it by the demarcation test rather than the label. The usual marks of pseudoscience are claims presented as established without evidence, immunity to refutation, and no record of corrections. On each mark, this site's record runs the other way, and each point is checkable in minutes.
Nothing here is presented as established science. The site's own grading, printed on its main surfaces, is stated, dated and unproven, and the home page opens its claims section with “I have not found a new law of nature.” The falsification register publishes, for each tracked claim, the result that would refute it, reproduced verbatim, dated and hashed in a public falsification record. One registered claim has already died by its own test: the early 2.24 estimate was retracted when cross-architecture replication did not support it, and the retraction stands in public.
The honest concessions are also on the record, in the site's own words: the work is self-published, is not peer-reviewed, and the author “holds no institutional affiliation, no doctorate, and no journal's imprimatur, and the paper is built so that none is needed to check it.” The registered study designs are prepared as draft registrations awaiting human submission, the machine-readable registers are public, the reproducibility page carries instructions for independent replication, and the verification pages run in the reader's own browser against systems the author does not control.
Ambition is conceded; the subject is large and the site says so. But the demarcation question is whether a programme can be proved wrong, and this one publishes the instructions. A reader who believes the theory is false has been handed the exact tests to run, and the record shows that when one fired, the claim died in public rather than being defended.