well, i started this just for fun and learning purpose, I've never thought i could finish the whole client... i know how to do it, but i don't have the time to do it. =/
unfortunately, each detail would take hours. It seems pretty easy, but it is not, the difference between an alpha client and a retail is pretty big actually, too much testing.
so there is no ETA... I'm spending like 1 hour each day, i do it because it is fun, i test new protocols, physics integration system, etc.
about the open source, yea, that would be possible, i'm using OGRE now, so, no problem there! OGRE is probably the best open source graphic engine out there.
about the money, i dont need it, i do this for fun, and I haven't had a mu server before lol
probably the web and unity projects have an ETA, if they are using the standard well known GS they just need to code the client, enter/test/leave and modify it, which is great!
Using the original mu gs definitely saves a lot of time.