I appreciate you asking, but the GPL grants you explicit permission to do what you ask
As for the name, you have several options. You are within your right to keep the name, and release it under whatever version you'd like. However this is not the preffered method as it easilly creates confusion.
The two common ways of doing it is either by adding a suffix to the version (patchlevel) ie, UltimateIRCd3.0.1(Tsunami).YourPatchNameHere or renaming it entirely.
Common practise dictates that minor changes, where the IRCd is largely unchanged use the patchlevel suffix, and more extensive changes (in which the IRCd is normally forked and maintained as a completely separate codebase) change the name.
All 3 are within your rights as granted by the GPL, but id prefer you choose one of the two latter
Just remember that we cannot support modified IRCd's either way.
Happy coding and happy hollidays.