Got a couple more days to work on my project this month.
1) I added the full inventory with a crafting grid and made the crafting work, server and client side, so that even if you decompile the client, you can't sniff the crafting recipes from the source, since it only happens on server side... haha! >.< (totally useless but I thought it was funny)
2) Added a couple more weapons, such as a stone blade and a tomahawk as shown on this first screenshot.
3) Added craftable items such as big stone nails that you can craft using stone pieces and the tomahawk. I also added wood fences and walls like exposed on the second screenshot.
4) Added the possibility to place items on the ground.
5) Everything works in multiplayer and single player mode.
Far from being done, but at least progress is being made and it's very encouraging to see it work on many different hardware now! Thanks all for your support throughout the last 3-4 months.