For 8 years I had managed a site running a blog based on MT 3.2 and phpBB 2.x/3.x and the security and maintenance of these two alone was constantly annoying and complex.
Thus I picked WordPress as the replacement for the MT blog and were also looking for an option to replace the phpBB forum. I bump into bbPress which had at that time just become a plugin for WordPress and I found it could do ~95% of what my forum users would need.
Now I'm helping out moderating http://bbpress.org, helping out others where I can, writing custom filters and plugins for WordPress and bbPress and contributing back to the bbPress core project making bbPress better with every new version.
I didn't set out to learn PHP with any of the goals above, though I am now albeit at my own casual pace and this is in no doubt because of the excellent code that is bbPress and by proxy @JJJ's ability to write great documentation alongside the core code.