Hello Mark,
I dunno for the license aspect, but just adding a bit of color about the library itself. Their
GitHub has only 13 Stars / 9 Forks, with 1 main contributors and 2 others.
This means that the library will not necessary receive the security attention as a library like BouncyCastle / Apache Commons, etc. If there is a vulnerability in it, perhaps nobody will find it until 3-4 years, and if it is found, to hope finding it from scanners, we have to assume they have a security release process including CVE publication and also assuming the scanners will take care about their CVEs (normally that part is "easy").
IOW if we want to keep our dependencies safe, using only popular ones is a good practice.
Not blocking the request, just trying to inform about the potential risk I am seeing there ;-)
Wadeck