Vivecraft uses a system of patches to avoid distributing Minecraft code. This complicates the build process a little bit. IF you use Eclipse you can open the workspace found in \mcp908\eclipse. You ...
If you use Eclipse you can open the workspace found in \mcp9xx\eclipse. You will have to correct the library path for the vanilla jar and realms jar, and also add libraries for JRift, json, asm, and ...