It's solo friendly in that you can enter Bozja on your own and don't need to worry about PF or DF or queues.
However to efficiently deal with the content in Bozja, you will need to join a party once inside. So you will be constantly asking to join parties for Critical Engagements, or Castrum when you get there, or for farming and FATEs.
It's very common to just type "LFG" (looking for group) into say chat (when you're at the location with various other people) and then get instantly picked up by a random party, which then disbands once that current event has finished. People don't expect you to hang around for anything and yes you can just drop in for 20 minutes, do a few FATEs, a couple CE's and then bail.