Would that be allowed like the policy on Derpibooru?

Judging from the the title of the Booru, it encompasses all of the LPS brand (not just the new TV series, although that seems to be the majority of all posts). If the OC is related to the brand in some way, then it's probably fine.

I'd go ahead and post it, and see if it sticks.

You can post anything LPS related, or Pet-Adapted, or Pet'rized so long as it doesn't break the NSFW policy of the image board. :)