BKCommonLib has versioning on a per-plugin basis, so when a certain plugin needs version 2, and version 1 is installed, the server owner is automatically notified and the plugin is not enabled. This prevents the common mishaps with outdated BKCommonLib versions. If you develop a plugin that uses BKCommonLib, make sure you depend on the earliest version that still offers the features you need. This makes sure your plugin remains functional on older Spigot builds.