I'm not sure if this is very difficult to build, but perhaps it is nice to create an addon which switches the Font in a UI to DyslexieFont ON / OFF. This would make any forum more accessible for dyslectic people.
You may want to consider Open Dyslexic font instead. It's based on a similar concept as Dyslexie, but it's free.
The Dyslexie web license goes from 99€ for up to 500 pageviews/month to 249€ for up to 10,000 pageviews/month. It uses Cufon, which can make text hard to select for copying, and I've read that it causes problems for people who use screen readers. I think Dyslexie would be better suited for print use.