A few pointers. On the happy "yay we can use it freely" side, we have:
* RFC 6090
Pure gold! A catalog of ECC techniques which were published so long ago that they cannot still be under patent. It includes digital signatures and Diffie-Hellman.
* DJB's page stating that certain patents don't apply to Curve25519 (which you mentioned): http://cr.yp.to/ecdh/patents.html
* Jack Lloyd's statement that he avoided techniques newer than about 1990 in Botan: https://bugzilla.redhat.com/show_bug.cgi?id=615372#c19
On the sad "no we can't use it" side, we have:
* Fedora's insistence on removing all elliptic curve cryptography from their Linux distribution and refusing to answer questions about why: https://bugzilla.redhat.com/show_bug.cgi?id=615372
Regards,
Zooko