I haven't seen any download offerings for trial NW Java AS in recent versions.
There was a trial for 7.0 dual stack some time ago but I never used it, so don't even know what's included in that installation.
SAP NetWeaver 7.0 - Java and ABAP Trial Version on Linux - VMware Edition - Tips & Tricks
Alternatively you might check SAP cloud trial appliances
Free Trial offerings via SAP Cloud Appliance Library
I used it for deploying HANA DB, but it costs quite a lot to run an Amazon AWS instance.
If you are into BI - check Open SAP - there was a BI course so I guess they were providing some kind of access to test BI system.