StellatedCUBE

The online servers perform authentication with steam, so you cannot access them without buying the game legitimately. There is a 3rd party server that does not do this, which can be accessed with the version I linked above. However, there is very little online traffic there, so you would likely need to arrange to play with someone else.

The download for this isn't working.

Sorry, it seems I forgot a file in the latest update. It should be fixed now.

I made it.

There is a custom launcher here that will automatically fetch updates. It also allows applying content patches, and playing on third party servers.