S/MIME library: MPL/GPL?

In the code here:

http://lxr.mozilla.org/seamonkey/source/security/nss/lib/smime/smime.h

the GPL part is in "Contributor(s)" section (line 19 to 31).

I want to use the SMIME library (in the NSS part of Mozilla) in my GPLized
open-source project
(a certified email system).
For now we are using OpenSSL, but it's very slow on verifying incoming
emails, so I want to try
this SMIME library.

There are any problems if I use that library (*without* modifying it, only
using it) with the GPL license of my project? Note that the GPL declaration
of smime.h is in the "Contributor(s)" section...