This plugin provides PR companies and users wanting to pitch, a means to give an "elevator" pitch in 140 characters or less.
Unfortunately, yes. You will need to ahve two twitter accounts. One is the twitter account you want to recieve direct message pitches. Generally, this is your primary Twitter account. Additionally, you will need a second Twitter account. WordPress will, in essence, act as the Twitter client. Messages sent via WP-TwitterForm will be sent via this account.
Secondly, you will need to have PHP 5.2+. The reason for this is that JSON support is not inherently in-built to earlier versions - and I like JSON because it's lightweight and easy on the CPUs of high-traffic or weak servers. Easier than XML parsing anyway. This may be optional, in future revisions, depending on "consumer demand".
Lower versions of PHP, if you can get it installed, can use the pecl JSON module. This is outside the scope of this plugin though. Google it.