I think "server" is good enough for the appropriate audiences. (Not everyone knows what a server is/does.) However since the accepted term is now "instance" I think the best idea is to mix them up so that audience will be able to pick up contextually that they have similar meanings.
Adults continue to learn new words in their home language at a rate of about 1 word/week through life. ^[citation needed]^ Many of these words are related to changes in technology. It is not too much to ask for a person to learn some new vocab when trying a new tech. But, having the initial ideas presented in a framiliar way that does not require use of a glossary is helpful.