I've written code to allow the creation of checkbox fields for use in the custom user profile fields. Thanks to the structure of the user profile code, it's just a matter of adding a new directory with the appropriate files (/user/profile/fields/checkbox/), and adding a language file. There are no changes to existing code.
Would you like to incorporate this into the standard Moodle code? I may still have cvs access (source forge username: brian-king). Or should I post it on the Moodle Modules and Plugins site?
Thanks and regards,