Flint is a weblog creation wizard, which aids in the creation of a complete weblog. It requires a separately purchased registration code and has its own version numbering - currently at v2.0.2.
Flint was first introduced alongside Tinderbox v.3.0.3.
It offers the user 4 differently styled CSS-based sets of template and various other features (set as setting up Amazon affiliate links). The user need not use the defaults - the 'default' Flint output can also be used a design example and as a stepping stone to more complex or personally styled web sites.
The output is 'just' HTML and CSS and doesn't need to be a weblog - it may simply be a few static web pages, whatever you want!
Be aware that content created by Flint reflects the Flint version at time of export. If you've subsequently customised the output TBX (or HTML from that) and see a Flint version update, it is worth perusing any change notes to see what has altered; it may be easier to manually update your output than to export a fresh web site from scratch in the new Flint.
Flint was updated in tandem with v4 to reflect issues created by the introduction of $HTMLIndentedParagraphStart and $HTMLIndentedParagraphEnd attributes.
If you use a Flint-created TBX from a Flint version before v1.0.1 you should locate the note /prototypes/*CSS and open its Get Info window (Cmd+Opt+I) at the HTML attributes section and set the two above mentioned attributes to hold no value (i.e. blank/no text). If you're still unsure about how to do this fix, best to drop an email to support at Eastgate and they'll be able to set you right.
Flint was versioned to v2.0.2 alongside Tinderbox v4.6.1, presumably to account for v.4.6.x syntax changes.