Sharing content that is not yours is allowed as long as you credit the original author and don’t violate their terms/license.
- Third-party mod websites . “Converting” content from a third-party website for use in FiveM (i.e. vehicles) is allowed as long as you credit the original author with a link and follow their own terms. However, the release must include original content . That is, creating a FiveM resource with only existing files is prohibited. Only exception is if said author of third-party mod is the FiveM topic creator.
Source: Releases Rules and FAQ
As you can see its already not really allowed, provided that it breaks the original authors terms etc. and permission is received.