Bob's forum software is
Simple Machines
Another free, open source is
phpBB • Free and Open Source Forum Software
Both can be skinned and modded. You may be best to let someone set them up as no matter which you use, you have to build a database. Its not difficult, but it can be a pain if you make a mistake trying to diagnose the issue. When you have it set up, have them install the Tapatalk plugin so that your forum is viewable on that app.
With no disrespect meant to this forum, I would forego the landing page aspect and make your index.php be a direct to the forum subjects page. It is much better for SEO and gives more weight to threads.