jsPlumb consists of several scripts in development, which are concatenated together when it comes time to release. You can run this yourself on the source - you need Grunt and Jekyll.
In the main project directory, execute the following command:
grunt build
The output is written into ./dist. Subsequent builds will overwrite the contents of the dist directory.
1.5.0 introduced the ability to build custom versions of jsPlumb, omitting connectors or renderers you do not need. This does not, admittedly, save you a huge amount; future releases will take this ability a step further and allow you, for instance, to leave out the whole makeTarget/makeSource module, should you wish to.
Say you want to leave out the VML renderer, for example. You would do this:
grunt build --renderers=svg
If you only need the Flowchart connectors, you'd do this:
grunt build --connectors=flowchart
If you need only the State Machine connectors and no VML renderer:
grunt build --connectors=statemachine --renderers=svg
Valid values for renderers are svg and vml. Valid values for connectors are connector names, all in lower case.
Note It is important you do not leave a space between values for the connectors or renderers parameters. Grunt will get confused if you do.