the shelf prospectus is essentially a short form prospectus that allows a company to issue shares over a particular time period. So essentially Knight doesn't want to issue all of the shares now, but acknowledges it might want to when the time is optimal. An interesting thing about this is Knight's founder Goodman doesn't like debt. Instead, he's stated that he likes to issue shares when the stock is overvalued. So, this may be partially why the company is organizing something like this. Maybe he expects a bounce in price?
Keep in mind, this doesn't always just have to be equity. The company can issue debt securities as well.
The company's CEO is very well respected and has proven to be able to build a reputable company in the past. However, people have been growing impatient with the company for some time now. The insider purchase is the biggest in a while, and it's by the founder no less, but in the grand scheme of things it's quite a small purchase.
For me, a bet on Knight is a bet on Goodman. He owns a significant amount of Knight shares, and like I said has proven to build up a successful company before. It just depends if you think he can do it again.