Zippy Promotion Forums Thread Like Summary - Open Source vs. Premoum Software

Do you use open source software for your community or a premium software? What made you choose the software you are using at the moment? If you have used both, how do you compare them for performance and features.

I'm currently using premium software on a few of my forums. This one uses UBB Threads which is a paid software. I also use Woltlab Suite for Thee Zone, and currently use vBulletin for Glitch Talk. As for my other forums they all use free open source platforms or are hosted on free forum hosting like Forum Spark.