The current in-tree version of nxclient (3.5.0.7) depends on dev-libs/openssl:0.9.8, which is being deprecated. The current upstream version (4.4.1.1) seems upgraded dependency to openssl-1* This new version contains a LOT of bundled libraries, so some work to replace them with system libs is necessary.
Thanks for the report, though NX4 support is low on my todo list (and limited time available). I saw recently (can not find the post right now) that the nx4 client was losing compatibility with "old" NX servers, so this further limits its interest without a server, so I am merging both NX4 bugs *** This bug has been marked as a duplicate of bug 488334 ***