By definition, TTF and OTF fonts can not be "open path" like Cricut writing fonts. However, if you choose ultra thin fonts, you can mimic the look of the open path fonts because the outlines collapse on themselves depending on the size you are writing and the width of the pen tip. I have links to lots of fonts that work well for writing/drawing in a diecutter here
http://cleversomeday.wordpress.com/ttfs-for-diecutters#penfontsAll times are CEST. The time is now 20:13