Yes, Cycrex, alternate accounts are allowed to be used on this server.
The exception would be if you are using an alternate account to avoid a ban, which is what Endraruix did with DevLuna.
On many servers, alternates are not allowed due to powerful first-time-join-bonuses or joining factions to gain extra power, etc. On this particular server alternates are really only used by some people to sit at mob grinders from what I've seen. MCRPG also starts you off with very basic materials, so alternates don't really pose a threat to a team becoming stronger or anything like that, which is why I think they're able to be used.