@bytex64 @nina_kali_nina
Here's the site for EOTA with source and boot images for the last version: https://www.rbt.his.u-fukui.ac.jp/~naniwa/comp/OS/

As for CTRON, the TRON variant for servers and networking equipment that seems to be even more obscure than BTRON, I'm not sure how many implementations there were. Fujitsu made a fault-tolerant server based on the TRON VLSI CPU, running a CTRON-based OS, but I'm not sure if there were ever any other implementations: http://tronweb.super-nova.co.jp/suresys2000.html