Bolo requires version 52 or later of AppleTalk to run. The Mac Plus and earlier models do not have this version of AppleTalk built into the ROM. If you have a Mac Plus running System 6.x, then you will need to put the AppleTalk INIT into your System Folder, restart the Mac, and try running Bolo again.
Up to version 0.99.2 of Bolo I used to include the AppleTalk 52.0 INIT so that Mac Plus owners could run Bolo.
It took less than 8K of space in the Bolo package, so I was happy to do this.
Unfortunately, this caused some problems. Certain Internet ftp sites refused to carry packages that contained what they called "pirate software".
I contacted Apple about getting permission to distribute this INIT. Since it is available free of charge to all Mac users I thought it would be a nice gesture for me to include it to make people's lives easier, but Apple told me that I would have to buy a commercial license to redistribute it.
So, the answer is, if you have an old Mac Plus, you'll have to find your own way to get a copy of AppleTalk 52.0.
For what it is worth, this is what Garry Hornbuckle, Apple Networking Evangelist, told me, being as helpful as he could subject to the constraints of what the lawyers would allow him to give away: