Even is MineClone2's license is GPL or LGPL, I didn't or used a base of MineClone2 for my project, nor did I use MineClone2's API. I made something for MineClone2, not something from MineClone2. I have the freedom to choose my own license while making something for anything.
The purpose of the GNU Affero GPL is to prevent a problem that affects developers of free programs that are often used on servers.
Suppose you develop and release a free program under the ordinary GNU GPL. If developer D modifies the program and releases it,
the GPL requires him to distribute his version under the GPL too. Thus, if you get a copy of his version, you are free to
incorporate some or all of his changes into your own version.
But suppose the program is mainly useful on servers. When D modifies the program, he might very likely run it on his own server and
never release copies. Then you would never get a copy of the source code of his version, so you would never have the chance to include
his changes in your version. You may not like that outcome.
Using the GNU Affero GPL avoids that outcome. If D runs his version on a server that everyone can use, you too can use it. Assuming he
has followed the license requirement to let the server's users download the source code of his version, you can do so, and then you can
incorporate his changes into your version. (If he hasn't followed it, you have your lawyer complain to him.)
In short GPL == AGPL; with the AGPL having more strict requirements that the source (including andy changes) be made avaialble upon request.