If you really want to install OkapiLib v4 (beta), head over to the releases page. Currently a Release Candidate is available for download.
It will be officially released soon, just some more testing and documentation is needed.
To install, download the template zip package.
prosv5 c f email@example.com-RC2.zip to install the library into PROS.
Then, in your project, run
prosv5 c u okapilib.
That will upgrade okapilib in your project.
Note that many things have been changed, so expect something to break.
Look at the header files for documentation, or the docs that are in development.
If you encounter any problems, please make sure to let someone know, so that it can be fixed.
Don’t expect official support until it is released, but okapilib is happy to receive beta testing feedback.