There’s lots of buzz lately about the so-called “open-core” business model of Marten Mickos’s new employer. But this is nothing new. Depending on how you define it, InnoDB is “open-core,” and has been for a long time. The InnoDB Hot Backup (ibbackup) tool was always closed-source. Did anyone ever cry foul and claim that this made InnoDB itself not open-source, or accuse Innobase / Oracle of masquerading as open-source? I don’t recall that happening, although sometimes people got suspicious about the interplay between the backup tool and the storage engine. Generally, though, the people I know who use InnoDB Hot Backup have no gripes about paying for it.
What is the difference between open-source with closed-source accessories, and crippleware? I think it depends on how people define the core functionality of software. Some might say that backup is core functionality for a database; and others would point to mysqldump and say that InnoDB isn’t crippleware as long as there is some alternative.
I think InnoDB is an interesting case that illustrates what can happen when commercial and GPL play together. Part of that story is the appearance of XtraBackup, an open-source competitor to InnoDB Hot Backup. Everyone’s subject to the rules of the game, unless they restrict the “core,” which would make it non-open-source to begin with.