can’t help but think of it in a simple but ignorant way... why can’t you just pass the same username/password from SMF to the MODx username/password fields in the modx_ database.
It’s not that simple: SMF uses SHA-1 passwords, MODx uses MD-5. These are one-way cyphers and you can’t unencrypt them from the database easily. You have to override the authentication on one side, and that’s where it gets tricky.
It should be possible with the right forum framework that supports a third-party API for authentication, or possibly Open ID. That said, the direction that would like be most useful in the long term may turn out to be to build a native forum/moderation engine native to MODx to go along with the other tools it provides. Consider the following idea-dump:
[*] xPDO for database abstraction and future running inside Revolution
[*] WebloginPE for user/profile management, though this in light of how Revo handles things should be considered
[*] a forum display engine (this is actually already done but needs to be ported to xPDO)
[*] a forum admin tool built on top of ExtJS which is what drives the entire Revo manager
[*] a forum moderation tool ... could be inspired by the comment moderation tools found in Jot
[*] chunks to template everything on the display side: this would make it incredibly easy for folks to have truly custom, semantic forums
[*] phpThumb to handle image thumbnails and upload resampling
[*] a private messaging system that works with Weblogin PE (this has been done elsewhere and should hopefully see a public reveal soon)
An important question becomes what periphery "forum bling" needs to be implemented. I’d say keep it simple and just do a great job with the simple forum functionality. When Revo comes around designed from the ground up to use external authentication, someone can tackle a true integration with a system that supports such things. Then you could have the right tool for the job in all situations.
… I would be more than happy to help people make their SMF theme match their Modx theme.
Ahem, I know this great CMS software that runs SMF and recently relaunched it’s site. Looks to me it still hasn’t updated it’s forum template yet…