I agree that choice is good.
That said, so far all I've used to access fan made ages is ULM, which has been a good introduction to them.
Now that a year has passed since MOUL was shut down, I think I'll check out Drizzle and the Offline KI so that I can revisit some of my favorite MOUL spots (Minkata and Kveer to name a few. Bringing in the Myst V ages sounds exciting too.
I truly appreciate all the talent folks (GoW, GoMa and whoever else) that have put in the tireless hours into building the future of Uru. Once the Open Source Myst Online is released, we'll be a lot closer to making it a success due to all your hard work. Cheers!