Infiniminer is a block-based sandbox digging game that uses volatile server software. This means that after the server shuts down, the map resets - kind of like sandbox in Garry's Mod.
If you were looking for a server to play on but noticed Infiniminer 1.5 isn't listing any servers, then you're out of luck. We rarely launch the server so it's very unlikely it will be online. Though it is very easy to launch when required as the game is no longer developed.