D.J. Bernstein stated that he wasn't aware of any patents that applied to Curve25519[1]. This leads to the following statement in the GnuPG v2.1 FAQ[2]:
>For many people the NIST and also the Brainpool curves have an doubtful origin and thus the plan for GnuPG is to use Bernstein’s Curve 25519 as default.
>For many people the NIST and also the Brainpool curves have an doubtful origin and thus the plan for GnuPG is to use Bernstein’s Curve 25519 as default.
[1] http://cr.yp.to/ecdh/patents.html
[2] https://gnupg.org/faq/whats-new-in-2.1.html