Copying content from another site, would definately harm to site, atleast in terms of seo. But Is it legal to copy/publish press release (specially free one)?
Yes, you're allowed to repost a press release. That's their purpose. And if you look into any newswire you'll likely be able to find in their TOS that anyone submitting a release has to grant that permission.
Hence the words "press release." Heck, there are 1000s of websites out there that do nothing but post PRs as their content.