The license limit can only be changed by an HP CE, with the machine
shutdown and after they use a special program to get a new codeword
combination for your machine.  You would pay HP for each trip out to change
the license level.  Also many of your software products - both HP and third
party are licensed by the user count.  So the answer is no you can't do it.

Probably okay any ways, it sounds like you were attempting to address some
symptoms instead of root cause. There are third party packages and
contributed library packages which will terminate sessions if they have
been inactive for a set period of time.  That can help with some of the
session counts.  If you have session vt-mgr session that are not releasing
( in a reasonable amount of time) after the PC logs off, then you may want
to contact HP and verify that you have the necessary patches.

If you have development and production running on the same box, you can
probably save money by procuring a small 918RX,  and moving some software
development to it.  That should also make the production box more stable,
and faster.

Finally if you webify your current applications, you can have the users
connect via a browser and Apache on the HP e3000.  Internet browser
sessions do not count against the session count.