Talk to a lawyer (costs money) or use a similar free font. ^^^^ What Hitch says.
Bear in mind that: many apps don't show embedded fonts at all, old Kindles using KF7 don't use embedded fonts, modern Kindles always by default use the system font, the user has to explicitly select Publisher fonts and even epub based ereaders don't always use embedded fonts. Only subsetted rather than obfuscated fonts always work, if a publisher font works at all and is selected.
So:
1) Use a free font (especially for main body text), or a less restrictive one.
2) Always subset.
3) Always test on kF7 mobi and newer kindle (in system selected font) to ensure it's readable and headings etc not crazy.
4) Especially avoid annoying Apple, Amazon, Adobe, Alphabet.
Reliable legal advice from an expert in the field costs money. A random Lawyer that deals with car accidents or wills or house sales is no use.
I just checked three kinds of Amazon Kindle file. They don't open with an Archive manager after renaming to .zip, but there are free tools to unpack them. Removing DRM from the actual HTML is a separate task. Only KFX has more serious DRM, and you never get offered it if you select Download to PC to USB transfer to eink Kindle. A Fire is really an Android tablet with a version of the Kindle App.
Renaming a copied epub to zip simply allows an Archive Manager to unpack all the files. HTML, CSS, images, fonts, and the epub control and index files.
Our County Library app is Belinda Borrowbox, which seems to use epub & Adobe DRM. But the app just uses Times Roman, Arial, Courier and one other. No embedded fonts.