dont know what you mean as "support" - but from JH's point of vew - put up any application you like, as long as it doesnt clash with the agreement (eg: porn, apps etc...)
JH won't help you write the code either.
they seem to have a quite a bit of experience in many of the common forums, eg: webwizguide, snitz, soop etc...
my personal favourite is webwizguide.com, altho i feel support has gone down a lote in the last while, but the script itself is very easy to work with.
its ASP based with Access database, or SQL.
PHPBB is free and nice, too. As the name suggests, it uses PHP. The database is MySQL. I think you can even install it from your control panel with the click of a button and answering a few questions. You can read about it in the control panel manual. http://www.jodohost.com/hsphere/html/adding_generic_scripts.html#phpbb