IDL has been upgraded to version 9.1 on linux and MacOS.
Updated documentation can be found here
To update IDL on your Mac laptop:
First dowload and install idl91-mac-x86_64.pkg (Intel) or idl91-mac-arm64.pkg (M1/M2/M3)
then download and install idl_9.1_astro_laptop.pkg
At the end of the idl91-mac-x86_64.pkg/idl91-mac-arm64.pkg installation, the license manager will start. Enter alruba2.uio.no in the server field and click "secure connection".
After installation, the IDL start scripts for command line usage will be located in /usr/local/bin. You can also use the IDL development GUI by starting the IDL app in /Applications/NV5/idl/.
See here for how to use IDL outside ITA.