For OHD? A paid community support version that the gives you access to occasional playtests and lets you try the indevelopment version. There is also some singleplayer DLC I haven't tried.

99% of the time I play the free version, there are several modded servers that have consistent player numbers and the free version is obviously where the playerbase is so you don't have to spend money on OHD at all, the monetized parts are more presented as ways to support the developers and community if you love the game. If you don't buy OHD again at most you may miss out on the occasional big playtest with the developer that they are streaming, that kind of thing.

Idk, the developer wanted to make Project Reality but in a modern moddable game engine and yeah... that is what it basically is and personally I love it. It is easy to play with friends too since it is no bullshit free no account sign up no nothing.

I have hundreds of hours in the game, the game is sometimes janky, it has awhile to go, the graphics are good but not the bestest ever.. but as I said it just does what it says on the tin, and I love OHD for that.

edit there is an indevelopment metagame mechanism that will allow clans to play multiple matches against one another while tracking scores and effecting subsequent match conditions with previous battle results. This is a web browser type tool that is part of the supporter edition but is very early stage and it doesn't gate gameplay for players as it exists outside of it.