I'm guessing it will be one of the forums running vb 3.x/4.x + vbseo. Many of us became highly dependent on vbseo to optimize our sites for search. But the company behind it went defunct and there was no longer any support. Having such a crucial plugin that is unsupported is dangerous. It's the situation we were in. If it "breaks" then you would be SOL. And I couldn't see upgrading to vb 4.x or vb 5.x as a viable option.
Actually dragonbyte has a much better product for SEO called DBSEO - http://www.dragonbyte-tech.com/product/303-dragonbyte-seo/
That said both of these product pound server resources and are predominantly based on structuring URL's which doesn't work anymore and custom coding in your own SEO adjustments is key. Example.... try googling "bodybuilding forum" UGBB doesn't use either of these mods.