Some more things that I'll add to the final specification:
- The bidder needs to provide code or detailed instructions on how to move current database data to the new database.
- The software needs to be at least as fast and resource-light as SMF.
- I like how the SMF post composition page allows you to highlight text and then click a button to apply certain BBCode. This needs to be replicated.
- I mentioned this a bit in the OP, but to be more clear: There needs to be "weighted time online" and "weighted post count" in addition to the raw values. It should not be possible for a user to increase one of the weighted values by too much without increasing the other value. If you post 200 posts in 1 hour, your weighted post count should be 1. If you post 1 post in 200 hours, your weighted time online should 6 hours. These numbers should be configurable and should apply retroactively when changed (where possible).
- Time online should not increase if you're simply refreshing a page.
- Post counts should not be shown on topic pages, but should be shown on profile pages.
Another point is that people coming to the forum will expect certain set of features they encountered on other forums. If we don't have them, the forum will simply suck donkey arse from the point of view of users.
As I mentioned in the OP, the new software must support all of the popular user-facing SMF features.
I don't care much whether the software will be written from scratch or based on some already-existing software, though the base must be written very cleanly so I can easily modify it.