I have been looking for some free (and preferably open-source) collaborative software on Google but I am having a difficult time. Ideally I would like collaborative software what I can download without it being a trial or having to pay for a subscription; one that allows such tasks to be done with a team in private. My reasoning is so that I can have group discussions and perform group-oriented tasks with a team without having to worry about costs.
Does anybody have any recommendations for completely free collaborative software?
To clarify: my intent is to work with multiple people when making a videogame, so we can discuss ideas, share content like textures, models, videos, etc. I use a Windows operating system (Windows 10). I'm unsure about what the OS over the server would be but I assume it'd be only accessable to people who use the same OS.