Starting in 2006 with open source software, I went from MyBB, and thent to Phorum. I was stubbornly hooked on that threaded display format, but in time my community made it clear they preferred a linear layout. Phorum was fun, but I had to do a lot of template and script hacking to get it to do the things I wanted. As we grew, we became too busy for our shared hosting environment, and had to graduate to a VPS server. As technology advanced, the Phorum started to break and the primary developers had since abandoned the project and just one remaining person was trying his best to handle tech support issues. Realizing that I was dealing with dead software that had reached end of life, I knew my best option would be paid software that has ongoing development and good tech support. I did a trial of both Xenforo and Invision, and Invision was the clear winner.