We've made every effort to appropriately license our fonts so they are available to our users for commercial purposes. Font licensing has become rather complex and on occasion, we've had to remove fonts from our site at the request of the author.
If you are building your brand around a particular font it would be worth your while to purchase the font from the publisher directly. This not only ensures you keep access to the font but also makes it available to you outside of PicMonkey. You can upload and use your own fonts in PicMonkey.
If you'd like more clarification on a particular project, please feel free to send an example to the support team.