Definition #1 is, while imprecise, more consistent with OSI open source than “source available”; “intellectual property” is a set of exclusive rights, not the content to which the rights apply—“source available” provides the content to the public, but not necessarily any substantial subset (or even necessarily any) of the rights constituting intellectual property.

> Other people prefer to use other definitions to elevate debates.

No, they'd prefer other definitions to obfuscate differences, specifically, when trying to define “open source” as equivalent to “sourve available” to erase the distinction that having separate terms with distinct definitions provides.