[OJFord]

IMO it's fair to call it open source if you can reasonably use the open part of it in its own right, if the core stands alone and there's just some closed source plugins or whatever.

Where 'open core' is to be scathingly applied and '!= open source' etc. is, IMO, when you have a system with only some piece open, and other integral pieces not. Like an open backend but closed source clients, keys required so a third-party client wouldn't work anyway, etc.