In common terms, gamemode entities are entities which are required for only certain gamemodes. Certain of those entities are:
Any other entities which affect the core gameplay are not considered as gamemode entities as the objective of the gamemode can be achieved without them or they can't be modified in the mapping process.
The base entity only appears activated in the modes Capture, Regen Capture and Hold (plus it's variants).
As cubeengine.com has been DDOSed since
Sunday 6th of October 2013 Saturday 18th of April 2014, the master server of Sauerbraten and Tesseract are both offline, as well as the website of Cube Engine (2).
As there currently isn't any way for (new) players to report bugs or reveal their thoughts about Cube Engine (2), the forum of Quadropolis is temporary meant for such things as well (it actually always has been that, but rather served as a second try for players next to the forum of Sauerbraten).
Connecting to public servers shouldn't be a problem, but new hosted servers probably won't work (as they won't be assigned).
If you need any information about Cube Engine (2), your Sauerbraten directory should contain a folder called docs which has all pages of the website (except the forum of course).
There is no specific date of when cubeengine.com will be back online again.
Spread the word across the community.