All the bases on this site use MudProgs. Which was inspired by DG but is seriously lacking in comparison. And while I've toyed with the idea of porting DG to Smaug, I realized it would be a far better use of my time to embed a scripting language like Lua or Ruby into them. However, as I lack the time, and admittedly the understanding to accomplish embedding a language, It's on the back burner for now.
None of the bases here have multiple currencies, but there is a snippet in the files section to add multiple currencies. And I believe there is one on MudBytes as well. If it's not in one place then it's on the other. I know I've seen it somewhere.
For features, Yes, that would be AFKMud for certain. It's almost entirely using C++, only some of the codebase still const char* instead of std::string. But it has a lot more features, then Smaug. However for a Futuristic/Sci-Fi MUD a SWR or SWFotE is going to be a better bet. However, if you're looking for simplicity, SmaugFUSS takes the cake there. LoP is a little less simple than SmaugFUSS and has more features than Smaug but Remcon is always quick to answer questions, and fix issues found in it.
[Edit:] Oh, and no. None of these support HoT (Heal over Time) spells. Although it might be possible to pull off with the recurring spell flag. It's something I've been meaning to tinker with, but got distracted with the Star Wars MUD my wife wanted to open. And sadly the only DoT (Damage over Time) spell set up is poison, and it was hard coded instead of worked into the OLC Spells system.