One actually hopes that IMDB doesn't in fact have any claim on posts written by users that happened to be hosted on their site.
"...disable our message boards on February 3, 2017 but will leave them open for two additional weeks so that users will have ample time to archive any message board content they'd like to keep for personal use."
Note the "personal use" above. Is a website like MovieChat.org considered personal use?
From http://www.imdb.com/conditions , section Copyright: "The compilation of all content included in or made available through any IMDb Service is the exclusive property of IMDb...".
I did my homework before starting this project and I'm confident we're in a good position :)
The users did not give you permission to use their data, and you're not associated with IMDb, and therefore do not inherit the rights.
Lastly, IMDb specifically states that scraping or extracting data is forbidden without written consent.
I'm sure there's a story there since I would have thought the usual direction, even for a small aggregate number of eventual engineer-patent attorney pairings, would be reversed. Hopefully you can post an "About Us" on MovieChat.org at some point when you feel comfortable. Thanks!