A Farcaster client could run both an ActivityPub / Mastodon and ATProto / BlueSky server and do bi-directional sync at the client level.
Before and during ETH launch I worked for bigchaindb.com and with preparing a public network ourselves, we obviously considered ETH a competitor and were bummed by the deliberate market capture. Devs seemed shameless about their ambitions. But everything was so open and neutral that this rhetoric didn‘t last.
all msg are essentially user-signed jsons.. so should be interoperable in theory