Well, basically Wesnoth is the most successful open source game in my opinion (that is not equal to me enjoying playing it¹). So, what does Wesnoth do what we do not? I mean organisatorically speaking. Here follows a few things I’ve noticed. Something to learn from?

Code access
ââ€â€Ã‚¢ Wesnoth uses Subversion, TMW uses Git (so we beat them there

ââ€â€Ã‚£ In Wesnoth a coder gets SVN commit rights when a certain number of patches have been accepted (I believe it’s somewhere around three non-trivial patches), I am not aware of any rules/guidelines regarding this in TMW
ââ€â€Ã‚¤ Artists may get SVN access as well in Wesnoth, but other developers/artists happily commit their stuff fairly soon (in general) it’s been finished; it seems to me that TMW in comparison is rather slow to put finished media in the repositories
Art development
ââ€â€Ã‚¢ In general read Jetryl/Jetrel’s post «Attracting and keeping artists on an OSS game project», there’s not much else I can add
Organization
ââ€â€Ã‚£ Wesnoth utilizes several levels of user groups, used in the various communication channels (forums, wiki, irc, in-game), it is easy to see who has what priviligies, responsibilities and what you can expect from them; for TMW I think another user group on Mantis would be great for instance, something between Reporter and Developer (along the lines of Contributor), and the forum too would do well with a more fine grained user designation
ââ€â€Ã‚¤ The coding and art forums come in two fashions in Wesnoth: one normal forum where anyone can post and one restricted where anyone can read but only devs, artists, commiters, moderators, admins &c. can post
ââ€â€Ã‚Â¥ Several guidelines have been established for things like coding, art critique, playing, ...
ââ€â€Ã‚¢ I’ll refrain to compare the bug tracking as I haven’t really looked at it in Wesnoth, but I believe they have been fairly good at triaging, assigning and fixing bugs/features, something which is happening in TWM right now as well, something that hopefully will continue
Well, I do not know much about how the coding per se is working, but several tools have been developed to easen the development. One thing I know is that they have several translator tools which we may have a look at when we decide to translate things on the server.
Obviously I forgot dozens of things I have noticed at some point in time and there is even more obviously all those things I am not aware of.
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¹ Which actually holds true for me playing TMW as well...
Bam bam! Let the creative juices flow!