I should add that the folks pointing you towards a lawyer are not being helpful.
You should LICENSE your font to those who want to use it - its an asset, and it can make you money.
A copyright is intended to be filed BY THE ARTIST, for nothing more than the fee charged by the Copyright Office. If someone infringes, there are multiple ways to get them to stop without an attorney, as the THREAT of a lawsuit is far more effective than actually filing one. Once a letter is sent by a lawyer, the opportunity for “amicable settlement” of the issue is likely gone. If YOU send a letter, and THREATEN legal action if they don’t stop, you can save you AND them a ton of money, as no one wins when they walk up the courthouse steps.
I used to run the division of AT&T Bell Labs that made the “Unix” operating system. (Had to sell the whole shebang to Novell, as the free unix was getting better and better, and I had 5,000 employees to feed…) I NEVER went up the courthouse steps, not even with people who were clearly not paying all the royalties we were due, like Microsoft (Balmer, et al were the usual culprits), and SCO (Larry and Doug Michels).
Yes, I could have sued under copyright AND trademark violations, and I accurately joked that we had more lawyers in our legal/contracts department than most of our licensees had employees, but the reality was that my best customers were inherently the biggest under-reporting and under-paying “pirates”. So, we did a lot of audits under our draconian audit clause, but I NEVER sued nobody, as you can’t make money in court, and I wanted the licensees to make more sales, and more money, so they could pay me more money.
The punchline here is that Doug and Larry were SUCH big customers, they ended up buying Unix from Novell, and employing all the employees who stuck at it through all the upheavals, so they ended up being the best friends the Unix division (including the lawyers!) ever had.
Bottom line, you don’t sue your customers. Nevah evah.
Most folks nevah evah get it.