Using multiple meta tags with the same name is valid HTML.
But we don't know how search engines and other readers will interpret them. Either two meta tags will be concatenated or one of them will be ignored/overwritten.
Example: The PHP-function get_meta_tags()
will ignore multiple meta tags with an equal name.
To avoid possible problems I would recommend to use a single meta tag:
<meta name="copyright" content="Company A, Company B" />
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