What is the extent of 'you won't be able to join pure servers' ? I had just planned to be using OA on LAN and thats it.
Pure Servers have checks for loaded PK3s in use by server. It won't let clients connect if
1. they don't have the PK3 file the server uses
2. their pk3 files are different than the server
It also causes any additional pk3s that clients have but servers don't to not load, to make games more fair and prevent cheats like fullbright players.
Another thing to note is that automatic downloading can be enabled, and one could connect to a pure server on the internet running a game using the mature pk3, and it would auto download it.