NTRU – Software

According to Wikipedia

NTRU is an open-source public-key cryptosystem that uses lattice-based cryptography to encrypt and decrypt data.

…

Unlike other popular public-key cryptosystems, it is resistant to attacks using Shor’s algorithm.

NTRUEncrypt was patented, but it was placed in the public domain in 2017. NTRUSign is patented, but it can be used by software under the GPL.^[1][2]

So this quantum resistant crypto algorithim is either public domain – which is good – or it’s signing version is patented but usable in GPL-licensed software. I must